Possible problem, experienced advice needed!

Hey guys , I need an old hand to advise me here. I been growing a white label NL, and things have been going great , but of course I always end up getting a new problem of some sort at some stage and I may have problem.. it might be nothing but it might be the start of something, and if it is I would like to identify t and fix it asap. I looked at the plat abuse chart and it looks like zinc def, but zinc def goes the whole way around the leaf whereas this just affects the tips. The problem is only on the top 2 nodes worth of small undeveloped fan leaves, otherwise shes looking ok, I would just hate to see this spread. I started using half a ml/per litre of grow feed more than recommended, but it doesn't strike me as nute burn, but then it looks pretty healthy so I can't see it being a def. I was clinging to the hope that since they were young leaves they would correct themselves but its starting to look like a problem rather than normal. But then I'm not an expert and that's why I need your help...
The plant in general




Some affected and unaffected leaves.



Thanks for looking.

ive seen that as well after they get 2 feet tall , like yours looks , very very nice, I usually put them into flower and that goes away lol. but check this web site out ,http://www.cannaversity.com/cannaversity/article.php?id=057 http://www.growweedeasy.com/marijuana-symptoms

Thanks for the links, one of them the pics aren't working though . This girl is in flowering already, around 10 days. I heard nl stretches bad so I forced flowering early and she has got about 3x bigger already ,so that's why I upped the dose of grow a little as a preventative measure. It may not have been needed though so nute burn ?? Or maybe since it has stretched so much a deficiency is possible..or else it's nothing to worry about....

10 days in, she is probably still stretching and gobbling up the food, so I don't think it's a burn, and especially since the tips are yellowing, not browning.
Anyways, 1/2ml per liter isn't a whole lot when you come right down to it, that's only a little over 1/2 tsp/ gal.
If it was me, I would feed once more, since I can't tell for sure if it's lighting or the leaves, but some are starting to look lighter than the rest, like N def. starting also.
Maybe my chart will help ya better.View attachment 2640463

Its nothing.