Something sounds wrong. If you’re riding hard week after week, you should be faster after one week off not slower.
My normal weekly riding routine involves 1 or 2 mountain bike rides (usually an all dayer on sunday of 4-7 hours, with maybe a 1-2 hour midweek ride), plus between 1 and 3 road rides of between 1 and 4 hours. 2 days a week I end up doing commuting riding of an hour or 2.
Depending on how much you want to solve the problem, it might be worth using somthing like Training Peaks to work out how much stress you are really putting on your body. If I add up the min and max from above that’s between 7-25 hours of riding a week, which is a big difference. Of course you’re going to need to use a HR monitor and a GPS each ride to get a real feel as to how much consistent training stress you’re putting on your body,and that might be too much faff. But as things stand, something doesn’t add up.
Miss one MTB ride and my ability to corner anywhere near the limits of my theoretical ability evaporates.
I’ve no idea what my theoretical limit is, I know I don’t want to be anywhere near it though :)