O.k an update.
I believe the epsom has helped. What must have been the magnesium component of the problem looks better and most of the plants look a little happier overall. I think in the SLHs issues were mostly magnesium, and i now think in the WWs it is a combo of mag and cal to varying degrees. I'll quickly mention what i thinks happened and my short sprint down error lane.
I think I over estimated the contribution of ca and mg from my tap water. I'd read a lot of comments a la "I'm using tap water, don't need cal mag". So I though tap water + coc nutes + buffered coco = shouldn't have a problem. I did dose a tiny bit of cal mag for a while then stopped, but i'll get to that in a sec. Looking at my tap water analysis again...Ca 11.4-17.3 mg/L, Mg 4.3-5.2mg/L...the ca is 0.0011-0.0017% and mg 0.0004-0.0005%. Thats 11-17ppm and 4-5ppm. Shouldn't even factor in.
When a few rusty spots appeared I had just made 3 changes. Upped the nutes inline with increased growth, and increased amount of both drip clean and multizyme to follow H&G schedule more closely. I assumed the problem was the increased nutes, but i now think it was demand for cal mag as the plant grew surpassing what i was providing. I was giving an insurance dose of 1/10 dose...but I had held that dose steady since the start of nutes and as I had been adjusting my nutes up.
As I thought it was nute burn at first, I dropped the nutes which i assume made the problem worse and overall stunted growth further.
Ofcourse I'm not sure this is all correct, but its what makes the most sense right now.
I'm not sure that H&G is 10 or 11% ca, they were the only 2 mentions of ca% i could find. But thinking about that, if calimagic is 5% ca and dose is 1ml/L, then if H&G was 10% and dose is 2+ml/L.... thats 4x calimagic ever feed....yeah maybe not correct, right?
Anyway, can you guys pls look at these pictures. The WW1 has very small and thin, light colored new grow...and overall the leaves have remained small. Do you think this is the cal def component? Not something else i hope... On some of the newer/intermediate leaves you can see a pattern of yellow spotting... cal def? Thanks!