None of the posters on this thread have claimed to have used any of these methods successfully. Most likely that would lead me to believe that the sex of a seed is already set. If a plant is stressed or is grown in inhospitable conditions some if not all female plants have dna directions to form male flowers as well to ensure seeds.
All of the following is according to the article. Up to 90-95% of seeds can become female. The sex of the seeds is undetermined until the 3rd or 4th week of veg growth. So this is all for the weeks 3-4 but if this is a big change then that would probably be stressful too.
The following help promote females:
-Low stress including: no pests attacks, no fungi attacks, no mold, no irregular photoperiod, not under-watered, not over-watered, not pruned or topped, a cannabis friendly soil mix, not recently transplanted, no small pots
-high nitrogen levels
-low potassium levels
-high air humidity
-moist soil never allowed to dry but not over-watered
-low temp. 65-75
-use MH lights
-short day (14 hour)