Looks pretty good all things considered!
Where is the closet pulling air from and what's the ambient RH and temp? Is it 80º and 70% RH in the room outside the closet? Sounds like ducting is your problem most of all. An intake with a light baffle (you can use a cardboard box with other pieces of cardboard to block off light flow - paint the whole interior black) should make the closet the same as the room it's in.Not sure how to fix this.