Help Needed, Seedling Problems

[JungleRain]

I need some help with these seedlings,
they are around 1 month old and over the last week all the older lower leaves have been yellowing and dropping off, some of the top older leaves have a dark marble effect coloring whislt others are looking bumpy and crinkly looking.
could it be over watering??? I don't think its over fertilizing as I have been using 1/4 to 1/2 strength solution, perhaps not enough fertilizer???
Its effecting about 30% of the seedlings, mainly the older ones.
Here are some pics;



The Temperature of the box they are in has been constantly around 25c and the humidity around 70%...
Here are a couple more pics;

[Chilicutter]

Maybe you should try stronger fertilizing some of the plants and look what happen.
Looks lack of nutrients.
Lower plants look like they don't get enough light.

[JungleRain]

Hi mika
perhaps too much watering: I've cut down on watering already
not enough fertilizer: I've added full strength and some super thrive
perhaps not enough light: they have 6 x 4ft grow fluros over them now in an area of 500mm x 500mm x 1500mm
with lights on 18 hrs, lights off 8 hrs, so for now I'll raise them closer to the lights

Here is info on the nutes I'm using:http://ecoorganicgarden.com.au/

These are the nutes I've been using, so now I'll change to full strength!!!

[Jah]

Hi friends. That could happen if the soil became sour because of overwatering. There are lots of strange FX happening because of that but lack of calcium (that make leaves look like a spoon or a boat) is more often than others

[huntsman]

I need some help with these seedlings,
they are around 1 month old and over the last week all the older lower leaves have been yellowing and dropping off, some of the top older leaves have a dark marble effect coloring whislt others are looking bumpy and crinkly looking.
could it be over watering??? I don't think its over fertilizing as I have been using 1/4 to 1/2 strength solution, perhaps not enough fertilizer???
Its effecting about 30% of the seedlings, mainly the older ones.
Here are some pics;

I have the identical problem, but the best answer I could find on two other forums, was "It's either over or under watering". Let's hope we both get to the bottom of it! ;~)

[Fatalii]

Hmm.. I had similar results with UV-fluorescent tubes while back... the plants looked horrible.
But if you're using "grow lights" it shouldn't be happening.

If it's caused by your ferts, then there's something terribly wrong with it.

No over or underwatering causes symptoms like that.

[Jah]

J, that could if overwatering peat soil with lack of calcium buffer (dolomite lime or so). Believe me. We have really bad soils in our shops here

[Fatalii]

I've seen very yellow and bad looking leaves because of totally wrong ph with the soil, but never seen anything like that....