R they under weight

Well, you can't see the gecko, so I don't know about "them". But judging by the one tail you can see in the shot, it would help if you fattened it up a bit. Is it not eating? Or are you just not giving it enough? Try feeding some waxworms, they beef up pretty fast on those.
Always give as much as they want to eat. Leopards generally don't over-eat, so that shouldn't be a problem.
-Amy