physicist

@physicist, off the top of my head i think calmag, bioheaven and activera might all have magnesium. you should be watering with water around 6.0 pH btw. just dial all that in ... you might want to flush with only top max (which should be humic acid , but double check) to get rid of the surplus nutrients

@physicist, good question, only long answers for it though : basically it's still Mg related but now i'm less sure it's not an excess. Check your nutrients, calmag is a micronutrient , mg is a micronutrient, so look to see if you're giving several different types of micronutrients, what i can see is you're probably giving three different products with Mg, so it really might be a Mg excess, which is actually a pretty huge problem... DM me once you check i'll walk you through it :facepunch:

@CRiSPrGrow, thanks! Indeed i added Calmag a few weeks ago since some leaves shown some sign of Mg defficiency. Maybe now there is too much since tap water should contain a fair amount. I'll try to not use Calmag for the next waterings to see if it solves the issue.

@CRiSPrGrow, thanks mate, your answer made me realize that i didn't update the light schedule on the site. It has been actually 12 hours for more than two weeks now ( i have just corrected this). So, considering this, do you still believe it is a Mg defficiency?