I'm in coco. Week 3 veg Using Plant Magic a+b and root stim for the moment until they grow a little bigger. The base E.C of my water is 0.6 and I'm feeding at 1.5ec at a PH of 5.8.
you issue is likely multi layered
water your plants with plain water... take a sample of the run off that come out the bottom of the pot and test the EC and ph
when the EC comes back with a very high reading, (which im sure it will) flush/leach your medium with lots and lots of plain water until you get the drain water EC down below EC 1.0
your source water has an EC of 0.6 which is high... have you a water test showing whats in it? whats the ph of the source water? do you know if its sulfur water or iron water or hard water containing large amounts of calcium?
do you have any kind of filtration system on the water source, water softener or whatever
I don't often say this but you might need to think about getting a reverse osmosis filter and dilute the source water so its 50/50
half R.O. and half source water
what are the npk numbers on the fertilizer bottles?
post a picture of the entire plant