Hello! I am a bat biologist at the University of Michigan (from Indiana originally!). Do you still have the bats you collected/have you arranged to give them to someone? If not, I would be interested in collecting them from you (here is my work profile with my email listed).
I agree with previous comments here, that it seems related to heat. The photos you posted are of juvenile bats (pups born earlier this summer). The maternity colonies can have a lot of bats gathered together and thus can get very hot. The young bats can be the first victims of heat, unfortunately.