I gave my plants more nutrients than that wen they were only 10" tall and they didn't burn. Not sure what your problem is, but I don't see how you could burn your plants with only 500 ppm unless they're just seedlings.
are you flushing the old ferts out before you pour new ones in? If you water with 300ppm and they only use 100, and then you add another 400 you raise it up to 600. Make sure you flush before adding new ones to prevent this
are you flushing the old ferts out before you pour new ones in? If you water with 300ppm and they only use 100, and then you add another 400 you raise it up to 600. Make sure you flush before adding new ones to prevent this