Pyramid seeds there from and I've found it a very stable strain all the plants seem to grow the same. I added flower nutes quite early probs about 3 weeks old as wanted to see how quick I could finish it. I'm kinda stumped to be honest mate without being there and seeing it it's so hard to say I've read a lot of other forums with people having same issues and doesn't seem to be a definite answer anywhere. All I no is with mine that looked like that once I reduce the nutes it got better. Although it's not aesthetically pleasing to us unless it inhibits growth the plants will not waste energy correcting the leaf if it's growing and the leaves are generally green and healthy I wouldn't worry.