Problem with my plant????

Im growing a sativa strain, either thai or jamaican. Its growing seriously fast, but i have noticed that the leaves are growing with a distinct v shape in them. is this a bad sign?
Thanks for any help

What's the "v" shape in the leaf look like? Pics? Does it look like damage or does it look like a mal-formation, or what?

Yes we need pics.

does not look like damage. All it is is a v shape going along the middle of the leaf, with the sides of the leaf being raised up causing a v shape.
I think it might be just because it is growing so fast, and/or fast root production.
Also.
it is on its 6 developing node, and i have just changed the light cycle to 12/12, should i use epsom salts at this stage, as the leaves are quite dark green.