RO or soft water won't make a huge difference in your formula... I switched from hard water to soft water and didn't require one adjustment to the formula.
It might take months to see an outcome caused by it... at which point you can make an intelligent decision adjustment do your dosage or choosing adding cal mag etc..
If the GHE tripack is providing at least 100ppm of Ca, it's probably fine. If it's below that, i'd still wait to see symptoms but more likely to need a calcium supplement of some kind. Calculate ppm from the gaurnateed analysis labels. There are free apps and websites that do this for you.
some plants are more robust than others and despite any effort made to the contrary, there are inevitable deviations between one pot and another. better formulas, imo, will work on a wider variety of phenos, but never 100%. As long as that tripack works for 90% of plants, that's all you can expect for a one-size-fits-all.
Also, doesn't look like a caclium deficiency. Looks more like a root zone issue. Drying patter on the non-dwc plants looks like improper watering habits too or complications of tiny plant in a large pot.
This is 'soilles' and dwc together? There's no reason why the same formula can't be used for both. Again, points back toward irrigation-related. if not getting 10% runoff with the soilleess, nutes are building up over time instead of balancing out (usually a tad higher than the formula but doesn't keep rising over time with proper runoff). Trying to water a small circle just beyond canopy size is smart, but also need ot make sure that saturation goes all the way down and you get some runoff. Small plant / big pot is a pita worth avoiding. People think potting up slows a plant down, but that's bullshit. If someone stunts a plant from a simple up-pot, they should just stop gardening altogether.