Seedlings problem, please help

Hello,
I have deflasked seedlings of Phal. Hawaii Dragon Girl in July and they were growing quite nicely, but lately I notice random yellow leaf appearing on some of them.
It is usually not the newest leaf but still concerns me, since it was my first deflasking and I am terrified to kill them all.
What can be a problem?
Thanks.
Here are the exampes of such leaves:

[Connie Star]

Too little nitrogen, maybe? See First Rays free information on nutrition, or maybe the American Orchid Societys info sheets.
They look quite healthy.

Thanks Connie. I read through Ray's info on microelements and signs of their deficiency. Now looking at my seedlings it seems that they are pale too, maybe they don't get enough iron. I am using all purpose balanced 20-20-20 at quarter strength. Maybe it is time to get the ferts designed specifically for orchids.
Are there any suggestions?
I read a lot about benefits of MSU, but at the same time there were some horror stories about burning orchids with MSU.
Are there any other good ferts?

[Brooke]

If the yellow leaves are the oldest leaves I don't think you have a problem. Old leaves start to die from the tip toward the stem. I would be more worried if the tip was green and the yellow was next to the stem.

I don't know the pedigree of your cross but the color wouldn't bother me either. Many Phals are a light green as opposed to the very dark green. I've deflasked hundreds of Phals and yours actually appear quite strong.

MSU fertilizer should not burn anything if you use it at the recommended strength. I can only use MSU for pure water and have never had a problem with it burning anything.

Brooke

Thank you Brooke. I feel much better now. The parents are Penang Girl and DTE, I think they both have non-dark leaves. And they are yelowing from the tips.

[Brooke]

I currently have a Penang Girl cross, sorry can't remember the other parent, and it definitely has about the same color foliage.

Your seedlings look great to me and now you need to get another flask!

Brooke

Oh yes, I will! Just let the spring come...

[Mervin]

Newly de-flasked seedings will lose their 'baby' leaves which are normally long and narrow.

Broader new leaves will grow out to replace the lost.

Your seedling are doing what it's suppose to do.

At least that's what I have experienced.

Looking good !

[zxyqu]

I agree with Mervin. Seedlings dont have the roots systems to support lots of leaves, and as such, more rapidly shed off the lower leaves. So long as your top leaves look good (which from these pics, they look great), you should be fine. These seedlings look really nice.

[silken]

I have a Penang Girl and the leaves are almost lime green even kept under low light. Don't know about the other parent.