Questions about Sebright chicks, clumsy, pasty

[prepperchickens]

I decided to get a couple more birds after the tragic and soul crushing loss of both my little boys, my barred rock (2.5 wks) and my guinea (2 mos) males. They died protecting the girls, my little heroes. Amazing they will do that so young. Makes the fact that people off their roosters like mere nuisances even more sad to me. Anywho, I got two GORGEOUS silver sebrights, 1 week old, and to me it's already clear one is a roo. They also both have pasty little butts, or did when I got them.
1) about the pasty but- are bantams more prone to this? None of my others have had it. Is it because they're so short? They seem healthy besides that, and very docile. I've given them oatmeal, egg, acv, a nice bath and blow out (lol), but the little suspected roo has crusty butt again not on his vent but right under like his down is dragging too low to keep clean. Does that happen with banties? Also they both have gassy poop, lol, I can hear them whenever they go so I'm thinking they have a slight tummy problem possibly. But their poop isn't runny for the most part.
2) they are both pretty unsteady on their little feet. They can perch but I see them kinda falling over a lot and I'm thinking again it's due to their extremely tiny size and being so low to the ground but I want to make sure it's not abnormal.
3) sexing them is difficult I'm sure but it seems to me that the easiest way to sex any chick is to watch how they behave together no matter their age. One is smaller and has less defined edge outline lacing on it's feathers, as well as shorter wing feathers, but it's behavior is the giveaway. Baby Roos seem to be more pushy and friendly, less timid, this one is constantly trying to be underneath the other one lol, he like follows her around sticking his head under her belly and when she's asleep he tried to wake her up constantly. Basically male chicks seem to be the bossy assertive ones. He also scratches and struts a lot more. I was just wondering if anyone else sexes chicks via their behavior with any success. I'm new at this but I've been right 5/5 times so far. That is a pretty statistically insignificant sample size though lol.

 

[prepperchickens]

The first pic was of the suspected hen, this is of the suspected roo. If you look you can see his wing feathers aren't as defined nor are they quite as long. But considering they both grow up to have the same feathering I wasn't sure if it meant anything with this breed so I tried to judge on behavior alone. I always fall in love with the cockerels first, it's almost purely instinctual for me, if I'm drawn to a certain bird they're male and if I'm sort of bored by a bird they're female, lol.

 

[prepperchickens]

I would really really appreciate anyone who knows bantams well letting me know what's Nola because i can't find anything online about bantam chicks having special needs or development. My little boy is 90% of the time ok on his feet but every now and then tips over and quickly rights himself with no trouble. It's not increasing, he eats well and his crop is soft but not empty (feels uh, kinda like a, erm, testicle, for utter lack of any other thing to compare it to as accurately) and he does his little thing around the brooder, struts and scratches and always tries to hide his head beneath his sister. He will chase her around trying to put his head under her tummy. He has a slightly messy but still but I haven't seen actual leakage. I put coconut oil on his vent because after bath and blow dry it looked a bit sore so now I can't tell if his down is matted from leakage or just the oil. I gave him Braggs acv and a capsule of odorless garlic oil in his water, and some ground up oatmeal in his feed. Also have both a bite of scrambled egg and a couple tiny pecks of yogurt. This was not done it 1 day this is over the past 2 and their poops are firm mostly, not abnormal, but have been gassy since I brought them home. Little baby chicken sharts. They had pasty butt at the store which is why I got them mainly, they're tiny sebrights and I felt they were too fragile for all the handling and scary noises. They're 9 days old. They seem ok honestly, they're always cheeping happily and whenever they start crying I can pick them up and calm them immediately. They have fresh water, the brooder is 96 at the highest and 85 in the cooler spots. Do little bantams need moe heat due to their size? They would prefer I leave it 100 in there and when I caught it that hot I raised the lamp til it was 96 and they cried like they were cold but I refused to let them be at 100 ( I have two professional thermometers, very accurate) and they adapted quickly. The feed store always keeps them too hot.
By this age they should be at 90 but they start crying. My temp seems to be ideal and I'm like 94 degrees on my skins surface. They're so small they're the size of day old regulars if not smaller, but their feathers are like 9 day olds. Can't being small make them need higher temps?
And is it normal for short little bantams to be kinda clumsy? Like I said he doesn't struggle at all to get back up but it's like he's so short that his little tummy touches the ground and throws him off balance. His legs don't appear bowed and he perches fine and hops on stuff. He's the smallest of the two, his sister is a little better balanced. Can I help him get more sure footed? Is what I'm describing in the absence of apparent weakness or severe immobility normal sometimes, like for tiny breeds? I just lost my brave little rooster and male guinea to a predator and I thought getting a bantam roo would be a way to replace the "leader" without risking my regular size hens injury/ abuse later on from a big rooster. Plus I miss my boys, I find roosters valiant and noble and worth the trouble. Roos need loving homes too! So I want to help him however i can. Due to my recent losses/trauma I'm paranoid big time so even though he doesn't seem like seriously I' wanna make sure I'm not seeing symptoms of some awful fatal illness or inadvertent neglect if bantams need special care. Please share any experience or insight you may have about sebrights or bantams in general. This is only my third time brooding chicks and I'm new (experienced with other birds but chickens are more complex I find ) and keep hearing sebrights are like fragile and hard to raise up and so far they are the only chicks out of seven that have had anything wrong at all, even just pasty butt. The rest of mine were amaZingly stress free (guineas especially, they have like no problems ever ). I think I can cut it if I have the right information. Wild birds have so many fewer issues, you just have to keep em warm and clean and feed them and give a little affection and they're good to go, chickens can have a hundred things go wrong it seems, I guess because nature is no longer in control of the gene pool. And sebrights are the height of genetic interference from humans so I'm sure some of the genes that make them beautiful also make them delicate/less hardy. But I've heard so a here say they're a breeze, too. They're sweet for sure, so docile. But as tiny as they are I just can't believe they aren't more delicate all around at first. I've seen baby morning doves just hatched the same size as these 9 day old chicks! I keep thinking I'm gonna break their wings or legs somehow. Help!