no offense, but there's no mights about this one. see, the issue is grow medium density. if you are using a soilless mix, it is still potting soil. as I understand it, soilless just doesn't have much in the way of fertilizer from the factory. I guess that's where the "less" part comes in, in soilless. It it less the ferts. But it is also a dense grow medium that will trap fert salts. They don't all wash out with the run-off. If that were the case, your plants would never get any food at all. In hydro, you have to maintain an upper ppm level because the roots grow in nothing but water. But you can plan on a soil type of medium to actually trap nutrients for a period of time, the length of which depends on the variables - the exact type of medium, how much of it there is, whether you just water periodically or feed every time, the size and feed rate of the plants, soil temp, type of lighting. If you put the powder ferts like fox farm's fruit and flower or tree frog, or time-release stuff in the soilless, you can expect the fert to stay there for a long time, like the entire grow. One other thing is you have to avoid bad info and try to determine for yourself what's good cuz there's a lot of misconceptions out there. You can fix this problem by asking at a nursery how things work and avoid the hydro shop cuz those people tend to be a little confused, give bad advice. Buy their products, but don't ask for help cuz they're in place to sell stuff, not be accurate.
