Don't FOLIAR feed regular nutes, this will usually burn your plants.
I respectfully disagree with that assertion. I use foliar feeding, have used it extensively in the past, use it to correct deficiencies that I don't want to do a soil/root drench to try to correct. The issue lies with what you're trying to pass through those cell walls, some things can, some things can't.
I also disagree that you need to use foliar-specific products. Just use one that dissolves well and can pass through the sprayer, and I also prefer to use a horticultural oil as a dispersant/sticker/spreader.
A product I've just started using on Mary--Botanica Maxsea--GREAT for foliars, dissolves completely. Don't foliar at the soil app rate of 1-2T/gal, though. Not that I'm worried it'll burn (it hasn't burned any plant I've used it on, including my very expensive rhododendron that was going downhill til it got foliared), just that I don't need to use so much and I'm cheap. So much so that I don't usually use the recommended soil app rate for soil apps, I tend to go much lighter. For foliar I use it at 1-2tsp/gal.
The problems I can make out in that picture (it's difficult for me with all the reflective material you have in there) are leaf twisting and a little curling. Is that what you're talking about when you say you see problems starting? If so, I'm not so sure a foliar feeding would correct any of that.
As for transplanting from rockwool, I don't use it, neither do I use expanded clay pellets. Coco, perlite or soil for me.
