here is the deal...
DONT PLAY NICE WITH SPIDERMITES!
they will nuke your crop in an instance! Pick up some DR Doom and HotShots NoPest strips asap!
http://www.amazon.com/Hydrofarm-DDSMK16OZ-16-Ounce-Doktor-Knockout/dp/B002JU1QEI
Spray on day one, wait till day three and spray again. Should you...
Get your ph right before increasing nutes. Otherwise you just go from one problem to the next brother. With coco I would aim for a water/nute solution in the range of 6.2 to 6.5 before dumping it in. After you add the water/nutes collect a little bit of runoff from it and check to see what the...
CoCo assumes the PH of the nute/water that goes into it. (unless you supplemented it with lime)
So, you either have nute lockout from improper PH or if your ph is correct then those plants are seriously hungry. (I am guessing seriously hungry due to the purple leaf stems and veins and yellowing...
Your running RO water so those tips are not from chlorine or chloromide, that soil should have all the cal it needs for the time being.
If it were mine, I would drop the calmag and superthrive. (I only use that when doing a transplant.) Just use your ph water and see where that takes you...