Can't seem to break the cycle of poor performance

Could be running your workouts too hard, too frequently, not recovering enough.

Get some blood work done- anemia(low iron) is a real thing that can slow the best of them down minutes in the 5000.

Had blood work done and everything came back fine. Already on an iron supplement. Ever since coming back I have really only had 1 workout a week, and mileage has been half of what it was in previous weeks.

You have peaked. Your race took so much out of you that your immune system took a hammering.

Your post above suggests that you were in taper mode. This is what happens when you taper and race hard. It takes a lot out of you.

Now you have to recover and rebuild.