No
mate its canna coco pro supposed to be buffered ? From what i read a+b contains plenty cal ive put an 1/8th tsp epson salt per gallon for the mag am all ears for suggestions tho am a complete noob to auto? D
I don't know cana coco pro, but I would be surprised if it were not buffered. It should say on the package, or if that is gone, then on the company's website. I am also unfamiliar with Cana a & b, but I know that MegaCrop which specifically claims to have all the Calcium and Magnesium cannabis in coco needs nonetheless often requires help, and MegaCrop makes a cal mag addition for the purpose. Bottom line is different strains, different grows, different needs. Others on here might be able to advise on the Epsom salts addition, I have no experience or homework on it. Ratios matter though, so I would be tempted to go with a cal mag mix intended to do the whole job.
Since you are using good quality buffered coco you likely do not have a serious buffering problem, so I think just adding some cal mag should sort things. The one picture of leaves with light color between the veins is potentially either a ph fluctuation that locked out stuff like magnesium for a while, a magnesium deficiency, or maybe some of each. There is a good diagnostic set of photos on growweedeasy.com.
As for flushing with straight rain water, I don't think doing that is a good idea with coco once the plants are in it. If you figure you need to flush, I suggest that you should do it with the nute solution you intend to grow them in at the stage they are in, and continue flushing until the runoff is close to the same pH and EC of the input. Sometimes this takes a few gallons of nutes. When faced with this in my current grow, I probably put at least 6-8 gallons of nute mix through a ~3 gallon container before things were finally sorted. Also, I suspect that flushing with straight rain water could shock your plants, so I would not do it. Finally, a serious flush with non cal-mag treated water might bugger the buffering that you started with. I believe that I read on one of these sites that one of the good buffered coco brands warns about this.
Coco has its good points, but it is less forgiving than soil. Conditions in the medium are far more dependent on what you put into it than is the case with soil which does a much stronger job than coco does of buffering out the screwups and approximations. I am trying coco in my current grow, and now that I am into it, I would not do it again without both a pH meter and an EC/ppm meter. Controlling things without them defeated me, but with them, I got things back on track. I very much doubt that I would have without them.
Long winded blather, but if I were you, I would start cal mag supplements, ideally using digital meters to keep track of things. Please take all of this as a genuine attempt to help. Others on here and other sites have really helped me out, and I am just doing my best to return the favor. Good luck with it, I hope your plants do well and provide you with some great bud.
ppp
