The layer of sphagnum has no benefit, and holds too much water for frogs' feet and plants' stems. It is best removed and replaced with a layer of leaf litter a few leaves deep over the entire substrate.
It is hard to see in the photo, but there may be other issues to address. On the right side of the viv there is a depression, and the false bottom doesn't extend all they way. Is there a purpose for that? Looks like a problem spot, where water will wick up and keep the substrate too wet.
The frogs would benefit from many, many more climbing opportunities -- they are avid climbers.
What is the ventilation? Is there a fan built into the top (I see a cord). If so, is it screened off for frog safety?
That looks like a 10g fish tank. If so, considering a larger enclosure would be a good idea, both for floorspace and for vertical climbing. An 18 x 18 x 18 viv is a tolerable minimum size for Dendrobates species.