Leaves Turning Black

[Cwb18781]

Hows it going use to grow all the time but stopped for years i had some clones gave to me so i started again but one of them the leafs are turning black on not really sure what the problem is as u can see the others are fine any help would be appreciated

 

[013]

Hey CWB, welcome to 420! We need more info to better diagnose your problem.

what’s your grow media? how often do you water? are you giving them nutes? what about cal-mag? are you adjusting ph? what value do you set ph at?