Poor little guy. Please give all the info that you can. Looks like possible metabolic disease, mouth rot [ infection ] or some type of trauma. Is he housed alone or with another ? If so, separate the other ASAP.
How long have you had him, what exact type + brand lights do you have ? If you don't have the boxes the name + wattage will be on the side of the bulbs. Pics of the entire tank, including lights , will be helpful.
What exactly is he eating, how big are the bugs [ pics of them as well if they're dubias or crickets ] and do you use calcium supplements ? This is all important info .