I defer to experts like chrisb1 on this question, but just my opinion, if i felt i was close to wiping out this exceedingly resilient ailment, but possibly wasn't quite there, i would hate after 21 days invested to quit 5-10 days too soon and have it linger... as i imagine if you don't wipe it out completely it will be back in full force given time... and it sounds like you are feeling capable of continuing further.
It would be great to get the candida tested to be sure every trace of it was gone before ending the fast.