Does he sound "rattly" like he has chest congestion? If so you need to get to the vet asap and get him on a antibiotic.

If he is hot, there are 2 things you can do...... dampen the durface of his ears with cool water...not dripping just nice and damp....Buns lose heat through their ears.... Or you can take an empty liter pop bottle, fill it 3/4rs with water, freeze it and then put it on a towel next to him....viola!! he has his very own bunny air conditioner! This hot weather can be very dangerous for bunns so make sure he and Tyah are out of sunlight and turn on a fan if possible.