I'm one of the ones that had this problem. In my case I had the problem while using Grow Big. I was pretty sure I was over ferting but I did it anyway because the plants seemed to like it. I'm still pretty inexperienced and I need to push things to see how far I can go I guess.

My soil ph was ok. I figured too much of whatever (nitrogen or whatever else) is in Grow Big could lock something else out. Because I had ph problem with my last and first grow and the leaves looked the same. But I used peat moss last time because I didn't know any better and it was really acidic. And I used different ferts last time. This time my soil ph is fine.
Something else I should mention because it could possibly have some weird effects is that my ferts are a couple years old. I don't know if that would matter but I figured I should mention it if the intention of this thread is to try to figure out commonalities.