I have been using
Trifecta for quiet awhile, one of the things that the treatment plan tells you is not to spray the last two weeks of your flowering cycle. Of all the things I have dealt with PM was the hardest to rid my grow of. As soon as you harvest you should spend some serious time in cleaning. Every single surface with bleach water and 24 hours after with peroxide water. Make sure the bleach water is completely dried as mixing bleach and peroxide causes a gas. The most important things to control is your humidity and providing a fresh air flow daily. This means a complete air exchange and not just the air blown around by your fans. Make sure your ladies have air flow above and below and defoliate to encourage good air flow.
You may also try spraying at full strength which would be 2 ounces per gallon every two days for a period of 14 days. It takes dedication and determination to rid your grow of this monster. Do not reuse your soil or pots without washing.
Good luck!
Trifecta is without a doubt one of the finest organic treatments out there. It will do its job if you do yours. I would also suggest that until you are 100 percent sure you have this under control, even with a new grow coming in that you do the preventive once a week spray.