Magnesium deficiency? How to cure it?

Ciao amico!!! Le tue piante stanno benissimo.. Secondo me non è una carenza ma qualche gocciolina di acqua che è rimasta sulla foglia e con la luce ha fatto una mini-bruciatura.. Niente di grave continua cosi!!!

don't foiliar spray. even if it works slightly, it is a horrible way to give nutrients to a marijuana plant. roots are diversified at the cellular level to absorb water.. use those. leaves are not. if magnesium, i'd give Epsom salt (magnesium sulfate) at 1g / gallon dillution. there's such a thing as too much calcium, and less likely your other thing have a ton of sulfur - unlike ca which is in your ferts your tap etc... if you look over your ferts ingredients and there isn't much magnesium, you may want to add this 1g/gallong with your current feed.. make sure everyhting is mixed well before you add one to the other. (always) Even so, you could cause a precipitate. if you run into this problem with all plants, you need a different fertilizer (as in complete feed, not any one product neccessarily, although good products don't require things like "cal-mag"-like products). If your feed requires extra supplements, it's not a good feed. it is incomplete and will always have this problem. i got lucky and found something decent on the 2nd try. avoid liquids, avoid cartoon graphics on labels, etc... don't use FF trio, lol... that stuff is utter trash.

your plant is beautiful buddy :-) Cal / mag you should always do this :-) Best if you have osmosis water and mix the stale water for 24 hours (after 24 hours the chlorine has evaporated somewhat) to an Ec value of 0.2. Then add Cal / Mag until the Ec is 0.4. This is your source of water