Pretty sure that's the typical disease Otos get (may be called bloat but I've seen most people say Dropsy). I would monitor the bloat over the next couple days and look for eye bulging, protruding pieces of skin and/or redness of the body which indicates popped blood vessels due to the extreme bloating. I don't want to be a pessimist but I have a feeling it will die soon as I'm experiencing the same situation with my otos right now and all of my research contained the same result-death.
It is hard to tell from the picture if she is pregnant or sick. They look prety similar but you should be able to see tiny eggs near the base of her tail if she is holding. Mine are usually pregnant for anywhere between 1-3 weeks with a small pocket of tiny yellow eggs. No luck with any fry surviving in my community.
Your timing is perfect.. I did not realize it until u said something but I gave them a slice of zucchini two days ago. Trying to get them to drop. They(I had two like that) started looking better yesterday. They look much better today. Maybe bloat is constipation? Fresh veggies always help me )
I read your thread good stuff. But back to the vegetables. All of my ottos look way better today. They sure seem to respond well to good food.
I was hesitant to give them vegetables because I wanted them to keep my tank clean. But judging how they all look today I think I'll keep feeding them veggies. Besides the pleco and snails were also digging in..