chasv77answered grow question 5 years ago Add some bloom nutes to your feedings as well. That can also trigger the process.
On a side note, and some growers disagree, I always throw the plant into a 32-36 dark period, to help jumpstart the pre-flower process.
Mold is a factor they say, but that may depend on high (60-70%) humidity. If your grow area has high humdity levels, you may not want to try this.
I usually see pistils, 10-12 days after 12/12 lights back on, with this method.