Off color spots??

Ok, this lady is a bit over 3 weeks old

Organic soil, Roco... somethin, but it was all organic
100 HPS light (all I could afford, going to get some cfl's to add for flowering)
Using recommended Flora nutes

Everything was looking good until all the sudden I noticed these spots...

i'm not sure either but i'm having the same problem with one of my babies, she just over four weeks and on a few of her leaves are yellow spotting on the end of each leaf. only about three leaves have done this so far theres about eight fully matured leaves and second growth is well on its way.

forgot to add running 1000 mh room temp, hygro% and co2 lv are monitored i have a intake vent sys with a sepreate exuast fan and a oscalating fan down lower in the room..

It's hard to tell from those pics but from what I could see I would place the problem as either ph or nutburn. I would do a flush and feed plain ph'ed water for 2-3 days than slowly add nutes back. Hope this helps Good Luck