Help!!!

Sorry I have no pics at the time but I will have some up later if I get hold of a camera. Anyways I recently noticed some of the older bottom leaves looking kinda glossy. After a while the spots turned a gray color then eventually brown and crunchy. Now all the leaves, new and old, are doing the same thing. Plants about 2 months old and in FF Ocean Forest with FF Grow Big nutes. Any advice would be greatly appreciated.

By the way I used the diagnosis guide or whatever to see if I could figure it out that way but to be honest it seemed like it could be any number of deficiencies and possibly nute burn