Thanks for the input guys.

Gail- I only have the cookie sheet fully on top of the tank when they are eating flies, to prevent escape. When they are not eating I sit it on the top diagonally, so some of the air slits on the lid are uncovered, and this uncovers the slits on the sides of the lid too. This is how I leave it throughout the day, do you think I should change this? I do this to keep humidity in, but I don't want to have ventilation problems.

Jessalyn - I noticed that mine do turn a darker color when they are stressed or hungry. Thanks for the heads up, I will watch the remaining frog for any darkening.