Falta de Cal or NO?

Hey brother, from what I saw you're in week 2 of flowering. Personally, to prevent the green of the leaves from weakening, I add doses of vegetative fertilizers (nitrogen) in the first 3 weeks of flowering, starting with more and going to less, and with a maximum of 75% of what the manufacturer recommends. On the other hand, if you're using purified water, it lacks calcium and magnesium, so you need to supplement it through watering constantly. I hope I could help, have a great day!

You need to diagnose your problem. Check your runoff waters ph and ec levels. Ec drifting up then flush with proper ph water. Ph out of whack then flush with ph water until the ph comes out at the proper reading. Cheers