You should transplant to your final pot size before flowering so you don't cause them any undue stress. If you pots are really too small, and you have to transplant you should be fine. You'll just have to keep giving them plain water, or extremely light doses of nutes every other watering. Ocean forest has alot of food in it, so you probably won't need any nutes for two or three weeks. It depends on the strain as well, some like alot of food, while others are hypersensitive to too much food.