ive had a some what similiar event so i hope my advice helps. First i would feed them more often maybe twice a week insted of once. also pay attention to the frogs when you feed them. is the newly added frog eating more? that could be a problem. when i first got urlacher, he lived up to his name. he was skinny from the petshop however shortly fattened up like a true linebacker. However when i introduce his friend i started to see his weight drop. hes not as aggresive with food anymore the other one eats all the food.