I'm in 4th week of flower with Skywalker OG in Happy frog, using RO water with 5ml of "Calmag Plus" per gallon, Ph 6.4. I added 1 TBS of Earth Juice Rainbow Mix organic bloom nutes at 3rd week of being transplanted into Happy frog, which would have been 2nd week of flower. I'm in 5 gal plastic pots. In a 2x4x6 tent with mars hydro tsl 2000 300w led set at 65% strength. Temps. Are 75 degrees F when lights on- 70 degrees when lights off...45-55% humidity. Symptoms started with lightning of the green pigment on newer leaves...so I upped the Calmag to 7.5ml per gal., thinking it was the start of Calmag deficiency... leaves stayed the same followed by edges and tips turning yellow into brown. I had the same problem in Ocean Forest the last two grows, but had no problem with the first grow using ocean Forest. Last 2 grows had same problems around same time, so I thought I'd try happy frog since it is less hot than ocean Forest, and with my added organic bloom fertilizer I thought I would be good this time... NOPE, same problem. What am I not picking up on??! Just flushed them with 10gal plain 6.4 Ph two days ago...these are pics from today