Awesome pic, kind of looks like a pic Mike Novy showed me of a stack of Phyllomedusines. How big is your group? How loud is their call? Are you keeping them drier because they are new imports? I have only kept the common members of the genus (dennysi and leucomystax) but would love to branch out someday. Good luck with them, they look really healthy.
Four, I'm pretty sure I have a female though. I'm keeping them drier because last year I had one drop dead overnight in a humid tank. Then the rest developed bacterial infections. I can't really describe the call, I think there's one on Amphibia Web. I keep them well ventilated on paper towels and fake plants. Their tank is really ugly

I have a big waterbowl that holds a gallon of water. Once a week I empty it, fill it with a bit of water, pop in the microwave till boiling, wipe it out, and fill it with fresh water. They crawl in there nightly and exchange fluids etc.
I really love these frogs, they're even kinda friendly

In the wild they breed in piss-filled buffalo/rhino wallows. The tadpoles have the wood-grain look too. Roman mentioned he thinks they may dwell in tree holes in the wild, thus the casque and the wood grain skin. Makes sense to me, mine have a weird, kinda "humped up" look to them when sleeping, as if they "want" to be crammed in a crevice or something. JVK
edit Oh and one other thing, I do mist them occasionally, but when I had the heat mat on (it's only been warm here for like a week) I would dump a bit of water over the heat mat and close a plastic flap on the lid, sealing up the tank, and fogging it up. ( the lid is partially glass) I would do this a couple times a week.I did this at night before I went to bed.