The belly is dark yes. In one spot it is greenish. I think it might be too late I have already buried him. I thought it was IBD but I guess many snakes die in this position. Checked my other ball pythons by letting them hold onto my hand with their tail and pull onto me and they had no problem. No obvious signs. They are all acting normal, one is shedding atm. I'm only 16 so I can't really afford a vet visit I'll just watch them closely. Have you ever had a snake die randomly like this?