I can't really tell without film footage, but one glaring issue is the arms (as posted above), you are burning a ton of juice keeping them locked. Be conscious of your wrists, move your arms so that the wrist is not angled so bad.
I just corrected a rider's numb hands issue by moving his brake levers, so hand position is extremely important.
Lastly, you do not appear to be relaxed at all. Easy fixes.
Good riding.