If he is eating any that is at least something. Try to reduce stress as much as possible by: not putting to many crickets in the tank, make sure heat is adequate, the tank is not exposed on all sides to movement in the room, etc...
If your leo doesnt seem to start eating more and its tail starts to thin, there is a product called 'Jump Start'. It is a thick cream that is vitamin enriched and will help to stimulate appetite. You have to force your leo to eat this using a suringe. You can put it in its mouth or around its lips (hopefully licking it off).
I had a leo that I had for the most part given up on. He had grown so thin and wouldnt eat anything. He is now my biggest and healthiest male thanks to Jump Start!! Good luck...