Possible ph issues

Hows it going. Im running synthetic nutes with coco for the first time in years . im using coco loco and general hydroponics flora three part plus calmag in RO water . I just potted them in four days ago and fed them with 600 ppm of nutes ( wishing I would have fed a little lighter) . i haven't used coco in a while or synthetics but i recalled the run off coming out high the first few feedings because of left over salts in the coco, so i PHd the solution to 5.6. Run off came back 5.6 , i was hoping for 5.8-5.9. i seen a tiny bit of tip burn the next few days , but not much . i sprayed them 3 or 4 days ago with "mammoth cancontrol" its pretty much corn oil ans thyme oil. The next day I noticed a bit of curl. It lasted two days and today i went in there and the curl was pretty much gone but where the leaves where curled, there is now some sort of burn . i was first thinking it was from the spray , but it looks more like a PH issue . please let me know your thoughts and giving me some opinions . thanks guys

I use mostly soil but to me your right on about a PH issue. The fact you have the reds on both your stock and leaf stems including the veins of your leaves along with the necrosis usually indicates a phosphate issue. So either bad PH is blocking P absorption or your medium is lacking it. Since your using the 3 part GH the problem most likely lies in the PH....sorry I couldn't be more help as I'm unfamiliar with using coco as a medium.
Cheers!