Something happened three days ago. pls help

[Roy Growin]

I tried this line of nutes last year and had same results - yellow, sick looking plants
As soon as I reverted to Canna they started to grow properly again
So my guess is that AN pHP does go off - stop using it

 

[SmokingWings]

Wow that yellowing is just from the past 3 days?? Crazy! Have no fear let's save your plant!!! @SmokingWings

The first batch of photos looks like maybe the start of a Calcium problem. It sounds like a grow in some sort of hydro set-up and I am not as familiar with those. Plus the mention that Calcium is already being added.

Then there is the one plant that is as yellow as the center of a traffic signal but the original poster did not ask about that. High amounts of Calcium in soil can play nasty with the pH, not sure about water based styles of growing. Plus all that Ca also messes with the Nitrogen and lack of Nitrogen causes yellowing and way to much N will burn a plant and turn it yellow but a different shade.

 

[Wastei]

Mixing organic additives with synthetic formulas is a recipe for disaster in a very passive system. The nutrient and its additives are asking for runoff at every feeding while OP has zero runoff to replenish the medium ending up adding excess and organic amendmendts that goes acidic with lack of oxygen.

If you want to run a completely passive hydro system it's better to add oxidizers, they will help add back oxygen to the root zone and kill of any nasties. You're better of like other suggested to run a completely synthetic formula without any organic amendmendts, it will be way more pH stable. I've used regular bleach since forever in hydro, you'll find the calculator with recommendations in my signature.