Rain rot or what?

couple weeks ago i noticed flaky and kinda bumpy skin on his elbow (both sides) going down his fore arm a little. i started putting mtg on it and it looks like it has dried up a bit. its like pieces of yellow crusty skin. i keep it dry and only put mtg on it about every other day. what could this be? am i taking care of it correctly? i was thinking rain rot but idk for sure.