Mossy frog died...

I recently purchased a mossy tree frog at reptile show. It lasted about 2 weeks, was eating small crickets and sadly found it floating in water area today.

I set up a 12x12x18 terrarium 3 months ago, I tried to make it bioactive by adding pothos, lucky bamboo, and another tropical plant(think dracaena), I added pill bugs also.

I had land(ecoearth) and had the hydroballs as drainage, a reptifilter pumped up water which flowed into a small water dish 4x3 inch by almost 2 inch deep. This was tilted slightly to overflow into gravel to flow to drainage layer and keep water moving.

Humidity was around 80% and air temp ranged from 70 to 76.

Did I do anything wrong, or did I get unlucky? Maybe a sick frog..he was eating though.

Any other types of frog I can put in there that's easier? Red eye, or maybe a dumpy..
Thanks