Some kind of deficiency?

What is going on with this plant?

http://imgur.com/a/eUObA

do tell? what are you feeding it? what soil is it in? lights? temps? strain? no doubt its one of those

White widow from nirvana, 250 mh |(running 24h), hesi nutrients(no vitamins), temp 25-29C, PLAGRON Light Mix, in their 3rd week, don't know humidity

Please note that out of 4 plants only 2 tallest display these symptoms

I really not sure but I'll throw my 2 cents in,
Looks to me like to much nitrogen, really dark Green like that, but that is just my opinion.
Good luck I sure hope you get it figured out.

Yup, looks like nitrogen toxicity, soil might be a little hot and adding nutes just cooked em up. Flush with PH'd water and look for signs of recovery in new growth .(not sure with nitrogen tox,but some deficiency/toxicity damage leaves never recover, so best to observe new growth).