Could it be that the high protein / low carb diet have something to do with it?

My money is on this one.

A few years ago I switched to a high-protein diet because I started lifting, slowly but steadily things "went south". At one point was pretty bad.

Then I found 1 obscure study linking low carb diet to low testosterone, I switched to a more balanced mediterranean diet and things improved and then got better than ever before.

I know this is heresy, but.. I am putting out there, you've heard it here first.