I can grow cannabis from start to finish indoors on two applications of fertilizer. http://www.mandalaseeds.com/Guides/Fertilizing-Smart-Guide
Yeah just ph water you could try a flush on your soil but really I wouldn't. It's better than nute burn, of course it's not what you hope for. One of mine is suffering from the same thing. Switching from pro mix to ffof takes some real adjustments.