have Potassium (K) Toxicity Magnesium (Mg) lock out

OK pretty sure I have Potassium (K) Toxicity Magnesium (Mg) lock out- in 4th wk of flower, have 10 plants 5 of which showing this problem all are indica prominent strain.
800wat HPS, 50% coco ,25% perlite, 25% vermiculite, 3gal grow bags. Using General Hydro Floro 3part. Waste to drain. Read Epsom salt will correct this. Have flushed with Ph'd 5.7 water. Will leave just drop off or will I see the life come back and the the yellowing dissipate...uuhhgg 1st time with this coco stuff.


http://www.greenmanspage.com/guides/plant_abuse.html#Heat_Stress (good source for Marijuana Plant Abuse Pics )
going to use 2 TBS epsom salt/gal .ppm is at 450 Ph 5.7 will keep posted of updated progress.
PLZ Shine in My ladies are crying. Sour Deisel, GG-14, KM Ualtra, Underdog have deficiencies other G13-WW, SD, Burmese Kush ,KillaWatt are fine same feeding as the ones that are showing problems ,

Hi eraxpar,
If your diagnosis is correct and if you lowered your bloom nutrient, then the plant should show recovery. Mg is a mobile element. But just throwing Epsom salts at it if the Mg is still locked out will do nothing.
JD