Black color on fan leaves

[Byob02]

im trying to figure it out what it is before it goes around my whole plant it look like mold so i pulled it off,
if any one can please help me out that would be great

 

[Byob02]

 

[CanniCulture]

Hey byob02,

The picture really helps people figure out whats wrong, but it's also best to include alot of extra information so we can really understand what your situation is.

I'd suggest looking at this page, and listing the specifications on your grow!

How to Ask for Grow Support

 

[thebeast27]

Id say thats start or boron defiency best of luck