more photos.first pic on the left is of the female.
The pic on the right, hanging on the screen, is the male? If he is very difficult to wake, it is worrisome because it means he is past the point of being alert to daytime predators (also the undue "tameness"). If he is just going to sleep a little earlier than the other, that is borderline. He may just be a small, elderly specimen. Also, hanging asleep on screen is something adult melleri do when they are emotionally stressed, have GI discomfort, or are otherwise compromised. Babies may crawl on and off screen in their curious ramblings by day, or be stuck there for the night at lights out, but adults prefer the comfort of big, solid perches to roost. Just an observation that sort of clicks with him going to roost early... something is "off".
If he's hanging on the screen because of close quarters with a dominant melleri, you can find your answer by separating them. I'm also a proponent of
responsible and carefully observed pairing and grouping of melleri, but you really can't expect two random animals paired by a dealer to bond automatically. It sounds like they were "paired" as a sales pitch, not based on any long-term observed behavior or clinical gender determination. I'd give the "male" a cage that is across the room from the other; on lazy afternoons, you can open both mesh doors and allow them to display and call to each other for gender clues. Your "male" may be ill and need to be kept apart, anyways.
As examples of how delicate pairing can be: I had one pair bond only after many weeks of long-distance views and displays. Another pair resulted after the female saw three males. These animals, like many, can be picky. Also, if these were truly subadults just out of the black-and-white phase, they would have no yellow stripes. Yellow comes to stay at 18-24 months of age, puberty. I think you have two small adults, age unknown.
Melleri have many displays, all along the Intense-O-Meter. A little breathing room for them, and quiet observation time, will tell you a great deal.