how awful my giants are still free ranging in the day even in this heat.. but they have an air conditioned home to retreat to which they usually do after about 2pm. also they are spending most of the day in the shaded part of the garden, you can actually see the line where the shade starts and they have been eating the grass there!!
so sorry, maybe he was feeling poorly anyway, bunnies are good at hiding illness due to being predators in wild, may have had an underlying condition so overheated more despite all the right care
its so sad because you see people who don't provide as much loving care yet get away with them in small hutches in full sun