Hot rocks are a very bad idea, they are too hot. What you end up with is one totally hot area, which can seriously burn an animal and ambient temps that are way to low.

If your talking about one of the half logs, they are not what you want either. Ball pythons need more cover than that. They need a hide.

Be sure you have an under tank heater, radiant heater or a room temp about 82. You then need a warm side of around 90 (this will be the under tank heater).

Have it set up so that your pet has a cool side hide and a warm side hide. Water bowls on each side.

I think fixing these things will greatly improve your snakes desire to feed. Once it's living needs are met and it has a place to hide ( ball pythons really need this) he should do ton's better