Seedling Troubles

My seedlings are about 2-3 inches from the top soil and on some of the seedlings the very first set of leaves, the one's after the seed leaves, are starting to turn yellow. This yellowing is not just in between veins but seems to progress throughout the whole leaf, mostly concentrated from the tip, progressing towards where the leaf connects to the branch.

One of my seedling looks completely normal with a healthy green colour, but the tips of the leaves, which grow after the seed leaves, are starting to turn yellow and curling upwards.


What could be the problem?

I've potted all my plants in an organic potting soil (.35-.5-.4) with Plant and aquarium flourescent bulb (5 ft. in length) going through cycles of 18 light/6 dark. I water them once the top soil, 1 inch deep, becomes dry to the touch. I should have pretty good drainage too cause i add 1/3 perlite to total volume of the pot.

I've thought about adding some fertilizer at half strength of (30-10-10) or Phosphorus rich fert. Should I add either of these next watering or just leave the plants.

How old are your seedlings? Don't add ferts until about one month. Do you ph test your water? How far away is your light from your plants?

I agree with Mogie. No nutes for the 1st month. Start out with some starting soil and make sure heat isn't a problem in your grow room. (Probably not because you're using a fluor.)

Well gee guys, I hate to be the one to disagree here, however if I am reading his soil correctly, it is extremely weak.
The general rule is that mobile elements N, P, K, Mg, etc. affect the older leaves first and the immobile elements like Sulphur, iron, calcium, etc. affect the new growth first.
However it is common for some mobile deficiencies to affect new growth. Given the timing I would guess a minor nitrogen or less likely Mg deficiency.
I would give em a low dose of nutes, like 1/4 strength, and see if it helps.
Peace

I just tested my soil ph and it should be around 7.3-7.5. I haven't checked the soil ph yet. The highest plant is pretty close to the fluorescent lights, about 1 inch. The temp in the room is 24 degrees celsius. The seedlings are between 3-4 weeks. My one seedling, which looked healthy a few days ago, is starting to get yellowish areas around the edges and tip of the second set of leaves. The yellowing always seems to be on the older leaves.I have 3 types of fert i could add. One is for acid loving plants, making soil slightly more acidic (30-10-10), the other is an all purpose (20-20-20), the other is (10-52-10); all 3 have an array mircro nutrients. Which of these would be the best?

dont use the acid one unless you reduce strength . and the 10-52-10 is a blooming solution use during flowering at half strength. i would reduce the 20-20-20 to half and use it as it is well balanced .goodluck

actuly if you used the 10-52-10 at 1/4 strenght it would be best the phos will stimulate root growth and the nitroge being at 2.5 will not burn your plant (sorry bout that first reply)

Thanks all for the help! I just added the 1/4 strength 10-52-10, now it's just a matter of patience to see the results.

Any luck? Post a pick!