I can garuntee the deaths are NOT from the temperature in the brooder or I would have had deaths a long time ago I’ve had over 200 chicks go through this brooder and the one in the barn and have never had a single death these deaths where obviously from something else a disease or weak genes from other people’s chickens because I have been hatching other people’s eggs for the first time lately. And no the cage is not over crowded if you look in the whole picture you can see they chose to all lay together there is lots of room to be spread out the fact you take the time to comment but not be helpful should have you removed from this page . You are the reason people are afraid or ashamed to ask for help when something goes wrong and you do not help with giving any insight on what actually could have gone wrong so why are you even commenting please remove yourself from my threads I will no longer be using this site and use the Facebook page as people there are actually helpful not useless and rude.
I've kinda read along on your thread as I enjoy learning from the outstanding experts here on the ER forum, two of which are really trying to help you.
I must say that just because you had no issues in the past with your brooder set up does not mean it is appropriate now. It truly is over crowded. And as @staceyj has pointed out, mechanical items can and WILL malfunction. You may have different air flow going through the brooder. You may have slightly weaker chicks that need things more "consistent".
Please don't be so defensive. No one here is attacking you and everyone wants what's best for your chicks, mostly you or you would not have reached out for help.