I'v grown many different auto strains, and never seems to fail, one is a marathon plant. The worst was an ak49 auto from vision seeds I cut it down week 17, never finished. No red hairs, trics were clear. Autos are fun but any more I'v come to believe its a crap shoot when growing autos. I went back to photo this last grow after 3 years of running autos. Sick of some finishing in 7 weeks and some take 14-16 or more. The last pack of Critical Jack heir autos I pop 5 seeds, (13 weeks ago) 1 was a mutant, 1 died (most likely my fault) 1 got 56g dry, 1 was 26g dry, the last is again a marathon plant hasn't started to finish yet at 13 weeks. I get their will be some difference from plant to plant and some auto are more stable than others. But sadly I think auto still are to unstable and vary to much for my liking when space and energy is limited.
Tho I have read that some auto need 12/12 to finish correctly, I'v never tried this method. If you try that method it would be nice to hear if it help or not. Sorry I cant give you any advise on how to get them to finish. But I can say I'm having and have had other that have acted this way.