Have you read some care sheets on these lizards? Are you using a UVB bulb and do you have a basking area where the temps on the surface are 90-95 degrees? Are you using calcium and vitamin supplements?

As to putting them together, it is not wise if you don't know the sex as males should never be housed together. If you are going to be there to watch them for awhile, then you can try and see how they act toward each other, or the safest thing to do would be to put the tanks together and see how they act with glass between to keep them from fighting.

Can you post pics of them? Post a pic from above if you can.