Yeppers.. have a female that I am conditioning to breed right now that I have to be careful on what I give her as anything live or homemade she will devour and then refuse anything else I try to give her. Which sucks as I need to give her the best foods, but can't let her wiggle her way out of eating certain other food that she needs.
Just stop feeding her the live food and just offer the pellets until she gets back into eating them. Continue this every time she starts to refuse.
Make sure the temp in his tank is 78-80, and that there is conditioner in with him.. Unfortunately I don't think there is anything you can give him to help - just keep him in warm, clean and conditioned water and hope he turns for the better.. I can't seem to think of a reason medication or a salt would help him any if he came into shock from the quick water transfer, I'm sorry :(