Yellow orange spots on phalaenopsis leaves

[chantrelle]

I have 3 hybrid phalaenopsis that have some yellow orange spots on their leaves.

It’s mainly on the leaves exposed to light (top leaves). I grow my phalaenopsis under T5 Fluorescents.

Here are some pictures

Phal II Spot by chantrell99, on Flickr

It is on the side of the leaf as it exposed to the light.
Phal
II side spot by chantrell99, on Flickr

The plant its self looks rather in a good shape.
Phal II by cha
ntrell99, on Flickr

Here it’s starting on another one

Phal I Spot by chantrell99, on Flickr

Would that be a virus, a fungus or due to the light ?