nute burn without useing nutes???

not a massive concern of mine was looking for a bit of advice.
i have 8 seeds going (12 days from seed) they are tora bora, bubblecheese,kushberry and R.K.S.

all is being done in coco, and every thing looks great with the exception of one of my R.K.S.

i havent fed any nutes yet and one of the seedlings has brown blotches on it with dark markings on the underside of the leaf. all the others are perfect lush green and the rest of it, but the R.K.S is being a right little bastard.

i dont know this is some sort of genetic defect or something more sinister. this is my 3rd grow, so im still relatively new but my growing conditions are perfect. +rep for any help

are you growing indoor or outdoor?

I had that same thing happen and i was told it was insects. If your not growing out doors then don't know but these were bugs in my case and i used insect soap. Worked slowly but surely

im growing indoors, cant see any signs of insects/bugs, does anyone know what sort of bug would do this?????. the leaves havent been eating or anything.

Is it possible that you've physically burnt the plant rather than chemical issues? How close are your lights? What's your overall heat level? Perhaps one of your strains is a bit more touchy when it comes to heat.

In the insect department, my usual suspects are spider mites or leaf miners.
Do your leaves look like someone spray painted near your plant and got a fine mist of white paint on them? This usually indicates spider mites. Leaf miners leave big ugly tracks.

Cheers!

Also, how do you water? Even check ph...

theres no white blotches, more of a fading to brown on the older growth, this did occur to me at first that it could be some sort of nitrogen dficency, but its so early on for that sort of thing.

there are 8 seedlings there, this is the only 1 with a problem, the other R.K.S is perfect. conditions in room are 25 lights on , 19 lights off, humidity is 58% and ive been keeping the ph at 5.8.. handwatering every other day with 15% runnoff. Using hesi supervit, rootcomplex and powerzyme. vegging under a 250mh.

i think i failed to mention that even though the R.K.S has leaf damage/discolouration it is still vegging at a good rate. thanks for the help guys . peace

Got good ventilation under all the plants? Otherwise i'd probably say ease off the nutes on that plant, leave the others going... and just see if it picks up. That particular seed might be more prone to the leaves drying...

If its still vegging like you said then I wouldn't worry about it. Its hard to say why one of the leaves turned brown, but hey... its still growing, so all is good.

I'd say keep it growing under whatever conditions your doing. It could be several reasons but if their no insects around you don't have to worry a lot.