I'm not trying to say that your care is wrong but I do need your care information to know if it is right. Many folks will say they are doing the proper thing but actually are missing something or were misinformed by others. Please do post enclosure pics, temps, humidity cycle, and feeding schedule.

That is not a normal looking vent by any stretch. I'd guess its either an infection or a parasite load of some kind. Are the feces runny? If you have a good exotic vet and have the cash I'd take it as soon as you can.