I wouldn't sweat the mother flowering , i had the same thing happen when my mothers were about 2 yrs old & i was running 20/4 lighting schedule .
I kept pulling 50 clones a week from them & changed lighting to 24 hrs a day , all the clones rooted perfect & i knocked nearly a week off my finish time , it took the mothers about 5 or 6 weeks where new growth didnt have bud growth but the strain retained its sexual maturity & it still finishes in roughly 7 weeks from 12/12 .
Strains been going nearly 5 yrs non stop at this point & the mothers are allways replaced with clones pulled from previous moms .