Green Crack

It's Usually around the 3rd or 4th week to start feeding, and when you do start with like a 1/4 to 1/3 the recommended strength when you do some nute brands a pretty strong. And with the size of your pots in consideration I would say start feeding around the 3rd week. Soils do have some nutrients in them and can vary how long they will last. so if you can look to see what and how much is in your soild. You are doing great plants look really healthy. Happy Growing! Hope this helps you an if you have any other ?'s don't be afraid to ask me or any of these other fine Growers😎

I've only forced outdoor plants into flower which was simply to bring them inside or cover them for 12 hrs of darkness but your situation must be very rare. Do what Crop King recommends and go from there maybe adding additional darkness will force them into flower. You may eventually want to try lower your Nitrogen and see if the additional phosphorous and potassium in bloom nutrient could also assist the plant to produce its fruits.