leave some green and a few growth tips after harvest.. go back to vege light schedule, but don't try to give 35-40 DLI.. tone it down a bit. reduce concentration of fertilizer too... and wait.
could also take cuttings off before harvest. maybe, this hedges bets a bit? but success rate with an already rooted plant should be quite high. could do both.. take a few cuttings, also try to revege the rooted plant... just need 1 to survive and kill the others.
consider breeding your keepers... or when you find 2 similar keepers, it doesn't matter. if you have good quality parents, youll have good quality seed. if you want consistency, try to breed 2 plants with similar traits. if you don't mind a little variety, the quality will be there, and you'll avoid all the work that keeping mothers is... it's a pain. also a disease vector, becaue they tend to stick around a lot longer than a grow cycle, obviously. time = opportunity