Well, for one thing, her days are way too long and, if I were you, I would shorten them [you need to do this gradually, only 15 minutes at a time every 2 weeks]. I would also try to imitate sunrise and sunset instead of just turning on a lamp. The specs on the full spectrum are perfect but I would put the light farther than you have it.
And, I might be wrong but that bird looks VERY uncomfortable upside down like that. I mean, she is like frozen in fear... legs up in the air and not moving at all. A VERY well adjusted gray might be OK laying on its back every now and then and for a very short time [seconds only] but doing it to a plucker that is having serious issues is not helping the bird at all - if anything, it would make the bird feel worse. Is it possible that she is not being treated the way a gray should be treated? I am not talking abuse or neglect, mind you! I can tell that you are trying your best but not everybody is a bird person... Parrots are not easy for us because they are not like dogs or cats and grays are particularly susceptible to reacting badly when they feel insecure, vulnerable or simply not getting the right kind of care. One thing I can tell you and it's that no gray would ever lay on its back out of its own initiative...