NFT system. Yellowing Leaves. Need help..

ive got a metre sq nft table. with 25 little girls in it.
They where transferred into the nft tank 6 days ago..
iam using canna veg.. ph has being 5.8/6.2. and the ec was 16 to start but has gone down to 15.. ive added plain ph sorted water to top up.
which ive done twice. but for the last few day 6/7 of the plants have started to get yellowing and curling leaves. more to the centre of the tank. i think this is nitrogen deficiency..
this is my first grow and i wanna get it right.. what iam i doing wrong.
and how do i fix it.
any help would be apprieated.....

I can't tell anything from those pics. I see some yellowing in the first pic, it looks like only happening directly below the lamp. You call it an NFT, is there a constant flow of nutes in the tank, or do you flood? How often?

I would raise the lamp some until I figured it out.

HTH

Thanks potroast..
Its proper NFT tank. so its constant flow. GTM2 heres a link to it.
leaves are yellowing and curling over. the veins and the stems remain green and the young ones are green.
and they have got worse since last nite. to being with it was only the centre ones.. now the others are getting it.

. i do think the light might have being a bit low. 8/9in..

Did you figure out the problem of your yellowing leaves.

cuckoo said:

Thanks potroast..
Its proper NFT tank. so its constant flow. GTM2 heres a link to it.
leaves are yellowing and curling over. the veins and the stems remain green and the young ones are green.
and they have got worse since last nite. to being with it was only the centre ones.. now the others are getting it.

. i do think the light might have being a bit low. 8/9in..

Click to expand...

did you figure out what the problem was? i had similar problems, it turned out to be a nitrogen and magnesium defeciency.