depends on how much they can uptake.. some plants are heavy feeders and some are not..typically when u see burnt marks on a plant that is cuz the ppm is to high ..in your case you growing autos.. ppm should range between 500-800Ok , well I got some Autos im going to be germ. in the next week . There be in 3 gal bags so what kind of PPM should I be looking at for them to be healthy