Yellow/Black Leaf Tip Help

OG Kush Bottom Leaf is turning yellow with black tips I think it might be low pH but not 100% sure. I need advice help me out.

OP , I get a this too, it doesn't seem to cause a problem, the leaves fall off eventually but everything seems to be ok. I reckon you start stressing when the rest of the plant looks like the bottom leaves.

Where's the black?
You sure it was black and not brown?
It's hard to tell what the tips look like when you cut them off before showing us.
Need info on the plant, not more, just info.
You don't tell how old, PH, what if anything you're feeding, soil, zero.