It doesn't need fertilizer right now, it needs to be nursed back. Don't make it work too hard for itself. Give plain water for a month and then maybe add some sort of rooting hormone only and weakly.

Definitely a victim of root rot from over-watering. In cases like that I put it in moist -not damp- sphagnum moss in a plastic bag -creates a humid environment- and hold the fertilizer and the water until new green roots get started. This can take a couple of months if it works, but I've brought back a few orchids that way. Good luck.