A bad weed never dies

Hello everyone! Since I was monitoring day by day the small nutrient burns on the leaves, I think I finally found out what's the issue: my nutrients don't work properly with the Hydro system, especially because they seem to be active for 48h top. So I decided to flush the plants for a couple of days while cleaning the water tank, and I found out that a lot of the "deactivated nutrient" (?) was on the bottom of the tank, which is probably the cause of the nutrient burns (in the last week, I cut down to 1/8 the dosage recommended, and still..) So, for now, I'll keep cleaning the water tank to be sure all the leftovers are gone, and I'll probably just add the bloom nutrient. After all, we're close to the finishing line, here. UPDATE: I went for flushing instead, water without nutrients, because I'm planning to cut the OS Younger by the end of this week. I still need to find a brand of nutrients that work fine with the hydro, suggestions are welcome.