Just my opinion, but crowding birds and a brooder that is too small is often a cause of many problems including: inability to correctly manage brooder temp (Providing cool areas as well as a spot to warm up. The entire brooder should not be warm) Crowded birds are more prone to illness due to crowding, and stress, more prone to behavioral problems including feather picking. Too much heat can also be a factor in aggression and feather picking. A crowded brooder is also more difficult to keep clean. I can't tell from your pic, but is the waterer raised up to standing chick chest level? A low level waterer is an invite to being soiled with feces, as well as the birds kicking it full of shavings, which will result in water wicking out into the bedding, turning the whole brooder into a wet mess.