I have or had 18 2 1/2 week old chicks in a large livestock watering tank(brooder) in my garage. There are 5 light brahmas,7 dark brahmas,2 SLW,3B Rand 1 NH. They are checked on many times during the day. Last night when I was putting everyone to bed for the night I noticed one of the lt. brahmas tail was red and a little bloody. I quickly removed it from the rest and an antibiotic ointment on the injured area and placed it in a small brooder by itself. This morning I checked the ones in the garage and everything was fine. I checked this afternoon and 2 more were the same way except not as bad and yes they are lt. brahmas also. None of the others are showing signs of this problem just the lt. brahmas. They were all hatched together so they are all the same age. What's up with this?