Why is my chick bald on her backside?

[TsBurks]

I got chicks from hatchery Feb 8, 2022
Lost 1 first morning after bringing them hom… couple days later, lost another… Then this morning I lost another…. Now, I noticed a bare spot on chick but when I took her out to check - she bald from her vent halfway down her fluffy butt…

HELP, What is going on???? I don’t want to lose anymore…
Last year I got 10 chicks from TSC and didn’t lose one…

 

[Wyorp Rock]

Is there a way to get clearer photos? The baldness, the brooder, the chicks?

Temperature of brooder?
What do you feed?

Are you using a similar setup you used last year? More chicks or less?