Thanks man! Yeah, some really knowledgeable growers on here. I try and absorb as much as I can. Definitely spent some time reading before even attempting a grow, and I kind of copied someone else. Figured it was a good guide. Ctrl-c, ctrl-v = plant!
I pushed the feed strength up from 400 ppm to 630 yesterday. Ran 1.5L through last night and just gave 1L today. Plenty of runoff which I tested and it was around 360 ppm. Definitely some rust spots on the newer but not newest leaves. Hopefully the new batch is what it wants.
Current confusion and thoughts:
If the runoff ppm is below what I'm feeding, does that mean the plant is using what I'm giving it? And should I increase the strength until I see the runoff testing close to feed strength?