So sorry to hear this Guy, makes us feel just terrible ( I know)

You mention they are having problems keeping food down, temperature is a big factor to look at for sure, but when they have worms they will throw up thier meals as well, and lose weight/ lethargic,,, so forth. You may want to get a fecal done on one of them, and see if they are having any intestinal parasite problems.
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PHEve / Eve