Molly laying at the bottom of the tank

[Mwoods]

I have three mollies in a 15 gallon tank and my only regular Molly started to lay on the bottom of the tank not moving just breathing. I did switch their tanks yesterday but he seemed happy and okay and now he is the only one just laying there.

 

[Colin_T]

what is the ammonia, nitrite, nitrate, pH & GH of the water?

can you post a pic of the fish?