I am no expert on what foods to eat to avoid depression, but I do know a thing or 2000 about depression, and after being on antidepressants for so long, being off of them for four months may not be really long enough to be really stable. Give it more time.
My depression is seasonal (Winter) so when I went off antidepressants I had to wait until the next Winter to see if I was okay (no). So, like you I made the commitment to become healthy. That's going pretty well, so I took more steps.
Right now I am reading books on ACT (Acceptance and Commitment Therapy) and it is really beginning to help me. Of course, exercise and eating cleanly will support any effort you make to better yourself, so you are on the right track there.
I personally wouldn't worry too much about the chemical imbalances that might be contributing to your depression, better to get as physically healthy as you are able, and then work on whatever emotional issues the depression is protecting you from.
My opinion only. Best of luck to you. :-)
Height: 5' 10"
Starting Weight: 292
Starting Primal Weight: 275
Current weight: 230
Goal weight: 172
Body Fat 27.5