I hear about your hard efforts and your high intensity days. I'm sure you pepper some really slow, ride like a tourist days in there if you have logged 4700+ miles in 6 months before.
Are you shocking your fitness enough? I mean, varying rides enough that you aren't stuck in a plateau that you can't get out of.

Your body composition has changed quite a bit. Is it possible that your bike fit is off and robbing you of that power or gear you seem to be missing?

New handlebar tape always makes me a bit faster....