Need some validation, please

[FarmHandSam]

Hello! I'm new here.

My son is almost 8, and an animal lover, so we decided a back yard flock would be a fun learning experience and a good way to teach some responsibility.
So, we've acquired 8 chicks. 3 bantams, 3 pullets (hybrids), and 2 leghorns.
We've got 2 with pasty butt, and every couple of days have been cleaning their butts with warm water and qtips. One of the bantams with pasty butt is definitely the runt. The others seem to have doubled in size, but that one (Siggy) seems to be around the same size. Siggy eats and drinks and carries on with the rest of them, just seems small. Do you guys think that's ok or should I be concerned?
Also, one bantam (Boneless) has a dead leg, for lack of better term. The foot seems turned in ward. Doesn't seem painful, but appears to be rather useless. Hasn't stopped Boneless from keeping up with the rest and seems to eat and drink well. Should I be worried, try to see a vet, or just let nature take its course?

Thanks for you time, and any feedback would be appreciated!

 

[TLWR]

You should be cleaning pasty butt more than every few days. Any time you see anything stuck to their butt, it needs to be cleaned off so it doesn't start to build up.

As for the little one, if it isn't growing, it may be a failure to thrive chick and nothing you do will help it.