New BP owner, have a few questions.

[CookieCutter]

I've had my smallest ball python (about two feet) for a month, and my largest (about four feet) for three weeks or so.
The big guy, Pierre, eats a LOT. I know that they'll eat almost every time you offer food, but he's active and acts hungry a lot. We've moved him up to rats, instead of lots of mice but he still seems hungry. Is this normal?
Jaques, the small guy eats 3 mice per week and is still sort of active but not nearly as much as Pierre.

Then ... one of my friends saw my snakes and fell in love, so he went to get some.
He got a tiny one first. She's about a foot long. He's had her for about a week and a half and she hasn't been interested in eating. He had mice that were bigger than her at first, so we traded mice 'cause we had some much smaller ones but she still didn't seem interested. She seems dry and skiddish. She doesn't look like she's going to shed, but is that a possibility?

The next one he got is bigger than his first. This one eats fine and isn't head shy or anything. The only issue with him is he seems to have a zit on the back of his neck, right by his head. I don't know how to explain it other than it looks like a zit between his scales.
Is this something that will come off with a shed, or should he worry?

Sorry about all the questions, I'm wanting to be sure all the snakies are fine and he doesn't have the internet.

Thanks everyone ^.^