Black Leaves anyone got a reason why?

Basically im growing Whitre rhino from nirvana. and im growing with a friend at his house. basically he killed the plant without asking me and whatevr but ohwell. it was weak and over stretched and fllopped over anyway but he said the leaves turned black on the top and were green on the bottom but wouldnt rub off. Any ideas what could have caused this? i had 3 plants going and the other 2 are okay. no possible wayt it was light burn. Does anyone know what causes symptoms of anysort of black matter that stays ontop of leaves? if so would really appreciate it + rep.

Sure it wasn't purple? I have a purple plant now that when you look at it certian ways it kinda looks black. Also I have green leaves on this plant too. not all are purple. Most are though. The mother went full purple even the bud by the time flowering was done.

Its white rhino, so i hope it wasnt purple. that would be great. It was a seedling so i dont know if it would show. It was like 2 weeks ish.

i've had some of my white widow leaves turn a dark purple black color when they get a little to much ferts,and the bud on the same plant is like dark purple black,covered in crystals

White Rhino is a heavy Indica strain which given the right enviroment, i.e coldness, will like many other Indica dominant strains turn hues of purple, blue and in extreme cases black. Do you have temp readout in your room or do you monitor them? If the plant has not been looked after then that will more than likely contibute in some way but abuse/deficiencey of plants will usually lead to yellowing/burning/wilting/drooping etc not black leaves. I may be wrong but it seems to me that your plant has been exposed to colder days/nights than it should have been or a mixture of both, hope this helps.

in my experience, the problem may have been due to overfertilizing. could this be the case? otherwise, maybe the PH was a factor. what soil were you using? if you used Miracle Grow with the ferts in it, that might be the problem.

Ph could have been a factor as i dont moniter it. Fert maybe coz my compast has a lil bit of fertiliser but most likely not the other 2 oare going strong. I think its the temperature maybe could that make it appear purple/black even if its a seedling with only about 4 leaves. Coz i believe it does get cold in lights out. so maybe? just maybe.