So I got three ball pythons about two weeks ago and one (a four month old spider) just doesn't seem to be doing well?

he won't eat and when he came to me he was already thinner than his clutch mate normal female I got as well which didn't really surprise me as males are smaller.
but the more I handle him (which at this point is at a minimal) I realise how skinny he is and after refusing to eat these two weeks, I wonder how long he can go on like this.

just now I was inspecting him and as he slid over my finger I could actually FEEL his heart. not just his heartbeat, but the actual organ.

he's weak and is a bit like a noodle

WHAT CAN I DO BEFORE RESORTING TO GOING TO THE VET?