The ppm levels presented are based on the percentages provided by the company. These percentages are actually made from a ratio based on an EC calculation. My EC meter calculates as a 0.5 ratio, while European meters use a 0.7. So it could be that there are more calculations which can be done to provide a more accurate estimate... lol.
If you take your final ppm of NPK, Ca, Mg, Su, and anything else, and double that number that should give you the uS. Divide the uS by 100 and you get your EC.
So a ~970ppm feeding could be a 1.9 EC (easily), and that's probably a bit excessive.
I have the CNS 17 coco nutrients on page 2 (among others). What I'd do, personally, with your stuff is more like a 12 Bloom, 5 Ripe, and 2 Hydroplex. This should keep your EC under 1.4, which is about as I as I think you want it. My run off has been in excess of 1,000 on all my plants, so if you're at under 1,000 in and 1,000 out, that might work out great, and you could have the right idea of ~970ppm with just a bunch of run off.
As I've been watering with 20% to 30% I've noticed the levels in my run off are coming down. I could have gotten a lot more run off the first two feedings in the planters they are in now. Run off is just too important to underestimate. In 4 or so waterings I should have balanced out. I plan on using about a 700ppm to 650ppm, 1.3 to 1.4 EC, for my full strength solution from here on out. Every time I go over 700 it seems like none of my plants benefit for long. It takes time I think for the buildup to have effect. Gradually I'll scale down to about 500ppm around week 7. Then I'll be doing 1/2 strength feedings like you are between the full strength ones. Right now my plants need a watering every 4-5 days in the 3 gallon planters. In 2 weeks that should be once every 3 days, and then eventually once every other day. At that point I'll feed full strength once a week and run half strength the rest of the time.
Over feeding in coco is just too easy. The media retains a lot of what you add. Run off is key to keeping the levels in check and keeping those girls happy. I wish I had all those drain tubs like you have, that's like $200 in plastic tub though.
Based on what you've been doing, and what you got going on, then I say don't fix it till it is broken. Your plan is as good as any other. Maybe your nutrients will work fine at that level... only one way we're going to find out
