Hello! Welcome to the frog forum !!

You are in the pacman frog forum, you will get better responses in the tree frog forum.

If they are both croaking then they are undoubtedly both males

Whites do like to change color. Although when they are not feeling well they do turn a deeper brown than normal. Can you post a pic of both the frog and the enclosure?

What are the temps and humidity?

Is the 20 gallon tank a 20 high? If not (and im sorry to be blunt) this is not an adequate enclosure for two white's tree frogs. Even in the 20 h two will not be happy. You should get an 18x18x24 tank at least.

Have you been dusting the crickets with calcium and vitamins and gut loading them?