Both of my BP's haven't eaten since November. I try to feed them every 3 weeks or so but they wont take it. Its not the first time its happened, though. Seems to happen this time of year, for me at least. I recently took them to the vet for a routine check up and mentioned they weren't eating. He almost laughed saying its totally normal (assuming their enclosure was up to par).
I say check your temps and humidity to make sure its ok and monitor their weight. Other than that, I say don't worry.. As for the rat, either return it to the pet store (I doubt they'll give you a refund now) or get yourself a small cage to house it. This has happened to me as well. LOL...