So one day of rest per week? That's reasonable if you started with a really solid base, but maybe the intensity has just caused this niggle.
One thing I have noticed (if you've been uploading everything to Strava), is that you're running everything at pretty much the same pace. You really need to make sure that your long runs are slow and that your recovery runs are even slower.
You're not going to add any fitness during your taper, so maybe cut it back to 3 runs a week and see how it goes?