Is this skinny disease?

Hello, fellow hobbyists! I got this cremesicle molly last week and she seems to have a sunken belly. I did some research and it seems like skinny disease. What do you think? And how do you think I should treat it?

She is eating as much as the others, but isolates herself - sometimes hiding under decorations and other times at the surface. She also seems to wobble slightly as she swims. I know there is plenty of oxygen in the tank, and water parameters are about as perfect as possible. 0 ammonia, 0 nitrite, 10 nitrate.