I think the heat lamp may be the issue---I found IMO that 91 ( even thought the "books" and "experts") say higher temps--that 91 degrees is too much--especially this time of year...I think they are getting too hot...try without--and if you need to you can always go back to the lamp...But I think if you take it away you will see it will help. I had my lamp on my "babies for the first few days at exactly what "experts" say and they were not happy--I went with my gut--took it completely off of them and they thrived...they did not have a heat lamp whatsoever from 3 days on...and they are now almost 4 months old and in outside coop and run. So if I can take a heat lamp off of 12 pullets in May--I think it's safe to say you can now...Just watch them--and you will know...Good luck...
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