Ok so you had said his casque started swelling so this indicates infection over obesity if it happened really quickly. Now the eyes specifically the one eye is concerning. You can see this with over supplementation of D3 and A but he is not getting that with you. So next cause for this is infection. Could be something going on within the eye. But you can also see this when they have something going on within the sinuses and that has in turn infected the surrounding areas. Meds to clear the infection would be a good route. But if there is something stuck in the eye he has to have long enough misting sessions to try to clear that. And this is the thing... those fake vines you are using flake off. The longer they are used the more they will start breaking down. So when he rubs his face and eyes on it risk of getting small pieces in the eye turret is higher.
Now UVB with a 5% T5HO bulb you want this distance to be 8-9 inches from the bottom of the fixture to the branch below it.
@elizaann2 can you post the vet list. Not sure if there is one on there that is near this OP but maybe.