Also if your using coco I like to do a nice flush right before she flowers to reset the medium. Whatever the amount of water you use to feed say 1 gallon for example times it by 3. So you would flush with 3 gallons of ph'd straight water. This helps push out any salt or nutrient build-up. The best wayg to see if you need a flush and if the flush got everything out is to test your runoff for both ph and ppm. A tds meter is a very inexpensive tool that makes a very big difference. I use mine everyday.