Looking good there JP! I recently moved to the 510 from LA and absolutely love the night temps up here, but quickly discovered the need for a dehumidifier instead.
Due to it's selective retention of cations, the best way to measure coco "runoff" is to take 1 part coco (from your pot, closest to root zone possible) and mix with 5 parts DI water, then test that.
Can't speak to your
calmag dosing cause I don't use H&G (yet...) but I don't see any problem with bumping your Mg to around the 100 range if you're seeing a deficiency (which I don't currently see). That sucks that H&G doesn't list Ca % and I couldn't find anything online. I don't know how companies get away with that shit.
Coco and smartpots for the win, indeed!