my seedlings are having problems with leave coloration, lack of growth, drooping leaves, and leaves are dropping in my greenhouse.

can someone help identify the problem.

i think it is a soil problem or a mite problem?...

I think it is a water problem. What is the source of the water you are applying to your seedlings? It looks like a high level of soluble salts. In picture number two what is the white crust on top of the soil? One symptom of high soluble salts is a white soil crustation, plus the common first symptom of burnt leaves. - Millet 88

This is a textbook example of high soluble salt content damage. I agree with Millet.

Kuwait uses sea water that has been processed.
It is very likely that there is still a lot of salt in it ...

i doubt that it is a salt problem the water i use is collected from my Air conditioner. as seen in the picture the lettuce and carrots are doing well.

The soil looks awfully wet and heavy. What are you using for potting soil/medium? Are you allowing the soil to dry out some between waterings? I do see what appears to be some sort of mineral accumulation on the surfaces of some of your pots, which is what I think others may be attributing to salt? Have you checked the water from the air conditioning to make sure it does not have other minerals or heavy metals in them? Something is bothering the citrus, and it looks to be coming from the watering to me as well.

bodavid, you say the water you are using comes from the air conditioner. Air conditioners don't change bad water into good water. The air conditioner has nothing to do with the quality, or the non-quality of the water. I think hoosierquilt is correct. Your seedling's problem is the water, PLUS as she points out the medium the seedlings are growing in is also questionable. - Millet 87

If it's a water-cooled air conditioner, then I agree with Millet. However, if you mean the condensate water from the AC, then it should be virtually distilled water, with only tiny traces of whatever dissolved from the pipes. I'm wondering, how hot has it ever been in that greenhouse? Significantly over 38C? It could be heat damage that you're seeing.

I also thought it could be sunburn.
Why do you need a greenhouse in Kuwait? Not much of a frost problem!

Before I installed a commercial wet wall cooling system along the greenhouse's south wall, my greenhouse would reach 110-F, and on occasion higher during the summer months. In my personal experience growing in my greenhouse I never had any citrus leaf burning at all, not even one time, even on my seedling trees. I did have some burning on the leaves of a few of my orchids. However, the extreme high temperatures did slow the growth of my plants quite a bit. It is certainly possible that Bodavid's seedlings could have suffered from the sun, but his problem must have also consisted of more than just that. Looking at the medium that the seedlings are growing in looks to be a real question mark. One last comment, after the instillation of the greenhouse wet wall I can now easily maintain temperatures of 80-F or lower during the summer. - Millet - 86

before two weeks i guessed that there was a problem with the potting medium ( 1/3 perlit , 1/3 peatmoss, 1/3 composted manure) . In the the past i have used sand instead of composted manure. when i removed some seedling from thier pots, i realised the roots were soaking in water.
therefore, i have removed most of the old medium then included sand in the equation. i started watering the plants with organic fish fertlizer. now there is a much better drainage. before two days there was good signs of new growth and they are strarting to become healthy.

thank you all for the great feedbacks

bodavid, what we first thought was the problem's delivery vector turned out to be different (manure instead of water). However, the original diagnoses of soluble salt burn was the problem. Manure is not very suitable for pots and containers, as it is too easy to cause burning. Generally, it is used only in soil beds. Glad your plants are on the mend. The best of luck to you and your young trees. - Millet 85