Grrr! Leaves turning nasty..

[Undergrounder]

I have a bunch of Phal. seedlings in a tank. The tank gets fairly humid, but i have a fan running for 15 mins of every hour which shoots down the humidity and provides plenty of air-movement.

In 3 or 4 of my Phals in the same area, some of the leaves (new or second newest) are starting to turn translucent and generally nasty. It's only happening to this particular cultivar, i haven't noticed it on any others, but i'm keeping my eyes peeled:





Any ideas?

thanks!

[snow]

what are they growing in? marble chips?

[Ross]

Not enough air. Try uping to 24/7 and see if this helps.

[Undergrounder]

Snow they're growing in perlite,

Ross does that mean you think its fungal? If i put the fan on 24/7 they will dry out, but i have changed the setup to give more air movement.

[Lagoon]

You can try to fan them crazy if you want, but without fresh air exchange you'll like see the fungus continue to spread. It's such a drag