I think i burnt my plant?? What is this im seeing??

Help me out what have I done to deserve this!? on the fist leaves and only on them, these brown spot showed up over night is this a heat thing, over water or nute burnt/def ?
thanks

[video=youtube_share;RP3aj_f2djE]http://youtu.be/RP3aj_f2djE[/video]

either nute burn or pH...seedlings this size should just now be getting their first nutes...so....

Yep i just put the nutes to her yesterday and now look what i have done I was a 200 ppm strenght for about 4 days and I turn the heat up to 700ppm yesterday. My ph was at 5.85 when i found the problem this AM

I flushed the rockwool with ph'd water and filled my res to bring the ppm down to 400ppm I hope thats enough? The other girl showed no signh of damage same strain just smaller plant?? This kind of stress is going to put her back a week isn't it!

Just chuck her some super thrive mate excellent stress reliever tried and tested in my journal take a look at one day after cuts and thrive man she look good could ov been just a bit ov moisture burn as its just on the first leaves Nute burn always start at tips new tips would be damaged if it was nute burn ?correct me if im wrong just my experience in a seedling like that bleaching would start also redding on stalks ect always best try avoid flushing for a few days man let it tell you its ill it just look like moisture off the hydroton to me .Peace FUGITIVE 360

The leaves are curling under a bit? but only the two big ones?