Try crickets. The crickets should be dusted. They will outgrow your tank. usually there is a min of 20 gal per frog. Some argue that a 30 gal tank for 2 frogs is ok but IMO the bigger the better. You also need to make sure they have access to water and that it's somewhat humid in the tank. I aim for no less than 50% humidity in mine. The moss is an impaction hazard. I would take it out. Give them time. They have been through a lot. Also, you might want to think about a quarantine tank and getting a fecal test done at your local herp vet.

I am sure others will with more knowledge will pipe up and add to this.

Congrats on your new frogs and welcome to the forum!

Here is the care sheet. Frog Forum - White's Tree Frog Care - Litoria caerulea