All of these posts and no definitive sources just opinions. Of course the imperial children had access to a good diet, exercise, good genes but you do have to wonder--out of 5 kids not one adolescent bump? And how advances was photo retouching? I've seen sloppy slashes of something like white-out and with electricity being pretty new how do you suppose anyone got hold of an airbrush?
Retouching technology was advanced enough at the turn of the century to significantly retouch coronation photos of Queen Alexandra of Great Britain -- bags under the eyes, wrinkles, and other signs of aging were entirely erased from photographs for public distribution. It wasn't unheard of for the Russian imperial family to have their formal photos retouched as well, though judging by their personal snapshots I don't think they indulged in retouching with the same fervor as Edward VII's wife.
For example, it's my understanding that Alix's chin was reshaped in this 1913 portrait:
I've also heard speculation that Tatiana's nose was retouched in this court dress pose from 1910 or 1911:
And I personally believe the details of the lacework on the girls' dresses were enhanced/highlighted in the 1910 session:
So the short answer is yes, I think it's entirely possible that any teenage blemishes could have been erased from OTMA's formal portraits.