Yes, the basic feeling here seems to be that you are using too much fertilizer- that the combination of all your fert components plus bushmaster, overapplied (too great length of time in your res and without dropping total ppms), has damaged the plants. Products like bushmaster and gravity are easy to overuse- you HAVE to follow label instructions to the letter.
You need a way to measure total fert ppm ESPECIALLY if using any type of supplement!