Well I just read your post again and the reason mine is the waye it is is due to my soils ph being to low. Yours seems fine. I probably would change your res. water and clean the tub and when you add the nutes, give them 1/4 strength for about 1 week and then gradually increase it. You might be right on the nute burn. I am not growing hydro so I am not too sure. I know you are supposed to mix the nutes in the water 1 at a time. Do you have any pic's of your setup?