They do like it hot, but too hot can kill them. If they are getting above 105-110 degrees, then that is too hot, but it would kill way more than just the adults.
It sounds like you just have a bunch of adults that have hit the end of their life cycle. Those may be the original batch you bought that are dieing off. But to be on the safe side, check through the enclosure carefully and look for signs of mold. Remove all the dead bodies and a full cleaning might be in order now too. If your babies and still surviving then I think you will be ok.