OK, so you switched to arrowhead water?
Whatever the case, your plants were doing well, then you switched your water source. That could be your problem.
Arrowhead is spring water. It COULD have sodium, or a ridiculous amount of Ca in it. Not sure.
If it does have sodium (Na) in it, it will compete with the trace metals, causing that lovely yellowing you see.
It will also get worse if you add nutes rich in Phosphorus, ie most bloom nutrients.
My advice would be to go back to the tap, and stick with it. (If it ain't broke, don't fix it.)
And I'm not 100% confident to say to flush today, but when the pots lighten up a bit, flush with distilled water. This will clear your medium, and you can start off on a clean slate for your next feeding. With tap!
This is tricky, though, because you don't know exactly what you are working with.