Help with Amazon Milk Frog

I am very new to keeping amphibians. I bought 4 amazon milk frogs about 3 weeks ago and am now down to one. The breeder told me they were 2 months old when I bought them and he is about 1".

He is in a 10 gallon euro style vivarium and was on paper towels. Heating with a UTH and thermostat keeping the tank about 78oF. I was using a basking light as well which would keep the top half of the tank where there were some branches ~85oF, but the bottom was 78oF. there was some sphagnum moss as well to help with humidity which was always above 60% with misting 2-3x a day. water bowl is changed everyday. they have a UVB bulb as well.

they were fed 1/4" crickets every night. What I may have been doing wrong here was taking them out to feed in a separate container. It seemed like the crickets were hiding in the moss, so I would put them in a plastic tub with vents for an hour or so to eat. I wore a glove to move them and they mostly would hop onto my hand. Could this be too much handling? or not enough time to catch food?

I decided to put a layer of cypress mulch patted down with a layer of sphagnum moss also patted down in the tank instead of paper towels to help with humidity.

I really want to keep my last little guy alive, so any advice would be great. I have just read about chytrid fungus...how would I know if this is affecting my frog? he does seem a bit lethargic, but I am not sure how active they should be.