Corn snake won't eat

[QuercusE36]

Hi, I'm new to the forum and have been a proud snake owner for 3 months now.
I have a corn snake (12 yo) and a boa constrictor imperator (15 yo) and suddenly the corn snake stopped eating. He's on a 10ish day feeding cycle and ate really well after first adopting him. Then suddenly he stopped eating bit has also gotten quite nippy. He not my niece and wouldn't let go, would bite at the water dish and today bit me as well. I assume he's hungry if he's nippy but won't accept food like before.

Things I've considered:
Nippy because hungry-won't eat mice like before
Doesn't prefer white mice-that's all he ate until recently. Gave him a black mouse and after 3 weeks of not eating he ate it. But today he didn't accept the black mouse.
Might be shedding-This finicky behavior has been going on for over a month and a half now and he hasn't so much as had clouded eyes or turned blue.
Metabolism slows down during winter-both snakes are kept in the garage (I'm in Olympia so it will never get close to freezing in the garage, not to mention the 100watt lights that are supplying adequate heat.

So, if my snake isn't hungry and isn't accepting food, why does it keep biting?