What is the black stuff here?

[Madtabman]

I had a deficiency issue due to a ph drop why i was away which has been rectified now and new growth is healthy. But Is this an old deficiency issue that has darkened over time? Or is it something else?

 

[bluter]

is the leaf lower or higher up on the plant ? a pic of the whole plant would help.

first guess is it's old damage but you can't get a diagnosis from a single leaf.

 

[Phytoplankton]

Could be an old worn out leaf, could be a number of things. More pics and your growing conditions, media, lighting, ph and nutes would be helpful.

 

[cbdhemp808]

Hey @Madtabman, The brown spots are necrosis—dead material. The yellowing areas are called interveinal chlorosis. Chlorosis is the technical term for yellowing. Interveinal means the area between the leaf veins. Some deficiencies show this pattern.

This leaf looks like a left-over from when you had your deficiency issues. Once there's necrosis, that can't be corrected—chuck it.