Diagnosis by internet is virtually impossible. However, I am extremely skeptical that your problem is attributable to COQ10, vitamins, suplements or similar things.
I can only offer this: Based on my own experience, any embouchure problems I have encountered from time to time seem to always be associated with too much pressure of the embouchure on the mouthpiece. I would suspect this even more strongly if you had been doing exercises to increase your high range or to achieve better intonation by focusing on a tuner while playing.
Are you having the problem EVERYWHERE in your range? Can you, by focusing a bit on relaxation, play the Blazevich studies? Can you play well below the staff (an octave or more below it)? Often switching to a different mouthpiece forces a kind of relaxation (at least for a while) -- until you get used to it and start forcing things again .
Just some thoughts.
Gary Merrill
Wessex EEb Bass tuba (DW 3XL or 2XL)
Mack Brass Compensating Euph (DE N106, Euph J, J9 euph)
Amati Oval Euph (DE 104, Euph J, J6 euph)
1924 Buescher 3-valve Eb tuba (with std US receiver), Kelly 25
Schiller American Heritage 7B clone bass trombone (DE LB K/K10/112/14 Lexan, Brass Ark MV50R)
1947 Olds "Standard" trombone (Olds #3)