@OrganicNature420,
Hi dude, nice to see you.
I'm following the advanced nutrients app recommendation, and I'm using distilled water (0ppm). So I would say it's ok to have 400 ppm on seedling/early vegetative state.
Indeed I have some leaves burned but I guess it's because I'm learning Hydroponics and finding some interesting problems to be solved. (High PH raised by the clay pellets, HI PPM as the water levels decrease during the week on evaporation and so on)
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