Phalaenopsis leaf disease - thinning, veinging and clearing?

[OzPhal]

Hi Everybody,

How are you all? My name is Dan and i'm comparatively new to the world of Phalaenopsis culture - although not new to Orchids in general. I have been growing Sarcochilus spp here in Australia since a young age. Sadly over time my collections has dwindled and i made the mistake of purchasing a Phalaenopsis spp a few months ago. Needless to say i'm now looking at importing species from Thailand etc and breeding my own (I'm a microbiologist by trade so do all my own flasking etc - i really enjoy it). In any case i have a hybrid, i'm not sure of it's name, and it has developed some clearing on some of its leaves, the veins are showing through and it almost looks like it's being dissolved from the inside. There are no mites or anything on the leaves, no fungus, any ideas what it might be and how to treat it? I've attached a picture for you to see what i mean...

Any thoughts?

I look forward to talking with you all more about the lovely Phalaenopsis...