Hey Has anyone considered the possibility its N tox, leaves that are not yellowed look that flat matt dark green colour, slight clawing on the tips. That would add up considering the ppm of the feed. The progression of N tox leads to the leaves yellowing in that mottled pattern and dying off. Plus you often don't see burned tips with N tox like you would with general nutrient burn. Could be caused from underwatering with high PPM feed
Anyhow, just something to consider, be interested to hear others opinions on that theory.
East side grower Yeah with hard water you need to use a light feeding, the harder the water the less feed. Depends whats in your water, you can google your water supplier to find out exactly what's in it. I have hard water and most strains like a light feeding apart from the OG which takes as much as I can throw at it.
Take what I say with a pinch of salt, I'm no expert but its worth considering the possibility before treating N deficiency.