New chick with sore bottom

Hello All, First time chicken "parent" here. We got four chicks last saturday- a Wyandotte, a R.I. Red, a Brahma and a Leghorn. We were looking for other breeds, but somehow wound up with these. Turned out that the Leghorn is a few days older than the others (and I have some fear that she is a he). Wyandotte and Red had poo stuck on and we cleaned them off with a little vegatble oil. Also added vinegar to water, gave a bit of egg (didn't touch) and fine cornmeal. Seem to be ok. Leghorn is strong- actually "attacked" me when I was holding the Brahma. Brahma also had poo stuck, cleaned off. Next day area seems irritated and "weepy". Cleaned again, this time with a scrap of cotton washcloth and warm water. Also put a dab of neosporin on last night and tonight. Chirped loudly-seeming to be in pain - that's when the Leghorn attacked. No obvious poo stuck, but streaks on feathers. All birds eating, drinking, sleeping, waking. Added another waterer last night with sav a chick probiotic and electrolytes. Any advice? Am I doing the right things? I will try to post photos in the morning. Thanks.

If the butt looks reddish and swollen, it may be a bit constipated from its vent being pasted up. Let the chick sit in a warm water bath up past the vent for at bit until it poops. The water will enter the vent and help soften the poop to allow the chick to pass it. You may have to do a little light massage to break it up, or if you can see the poop protruding from the vent but not going anywhere, you can very carefully pick at it with tweezers.

After the bath, dry the chick thoroughly. Make sure it stays warm throughout the entire process (but not overheated) or the pasty butt will likely recur.

Smooth some coconut oil on the raw vent. It's better than Neosporin. It has many more healing properties and may help poop from sticking.

Thanks for the advice, everyone.
Here is a picture (never dreamed I would post a picture that part of a chicken on the internet!) taken this morning. This afternoon she did seem a bit cleaner. Does it look like irritation from poop or something else?

It doesn't appear to be red and inflamed. It's hard to tell with her down in the way.

Just keep her clean and lubed, and she should be fine.