Strange hunger strike

[GoldSheep]

I have a very reliable eater male python. (Normal) and he's been on hunger strike (Spotty hunger strike). His behavior is kinda strange though.

Normally, he kills the prey, and then leaves it for a while, then eats it. This is kinda left over from his last owner, where he liked to pretend that it's dead first before eating it (She fed him fresh killed. Also said she bought him from Graziani). (His son does this strange behavior too, so I'm not quite sure if it's genetic or not--none of the other ball pythons do this, so I'm thinking it's something in his genes).

When the hunger strike started, the gap between him killing the rat and him eating the rat got wider... and then wider, and then he'd go through the motions, but not eat the rat. He shows interest in eating the rat and has all the signs of wanting to eat the rat, but doesn't eat the rat. He'd have it in his mouth, too, head first. Then nothing.

I've tried changing his hide, which made him cross because he really likes hiding on top of his hide.

I've tried adjusting the temps and humidity... but that doesn't do anything.

I've tried giving him smaller prey items, but that doesn't do anything.

I've looked inside his mouth to check for mouth rot, but I don't see anything.

I'm worried maybe he has an RI, but I can't tell if he's just super pissed that I'm handing him, or if it's an RI. (I have no idea how he'd get an RI, though.)

My female ball python in the same set up is eating steadily.

And the other male python is eating in his usual spotty manner. (Which drives me nuts).

This ball python is usually reliable, but as he hasn't eaten, I'm concerned.

He's about 8 years old, so I'm wondering if it's his age... (I've had him for 3 years of his 8)

He's losing a lot of weight, so I'm really concerned.

So how do I know for sure it's an RI? I don't want to take him to a vet too quickly, because the vets in my area are kind of expensive (100 dollars per visit, not including meds) AND I haven't found one that I like... (It's really hard to find an exotic vet.) And if it's not an RI, is there anything I can do to get him eating again?