Yikes, please don't use that terrible advise above.
Your medium of FFOF/Happy Frog is plenty strong enough to feed them for a while. You should only be giving straight water for several more weeks.
They look green and healthy which makes me think it's a watering issue. Are you letting the soil get fairly dry between waterings? It looks like they're trying to get rid of excess water, and your soil looks really damp.
Get your temps and humidity straight.