Nothern Lights Auto - Seedsman

Yes it would be a calcium deficiency at a early stage but can't be sure , you'r not running into a N toxicity to me BUT your plants are dark green so no problems if you cu a bit on the N in your feeding , of course purple light are well known to induce dark green foliage ( I've experimented it ((depending on the spectrum)) so it could be simply due to that fact. You' on the way and these issues are minor but can still be corrected. Free advice , in my opinion you can feed with a 1.8ec solution without seeing signs of over feeding