Phal with spots
 

I cut three very sad-looking leaves off my phal yesterday after months
of watching it go from bad to worse. See picture of the leaves in a post
with the same subject line in alt.binaries.pictures.orchids.

Can anyone tell me what the problem is? I can't find any creepy
crawlies of any sort. The plant has just produced one brand-new, green
and shiny leaf but it didn't flower this year. Not surprising.

I've already lost one phal to a similar problem and I see the tell-tale
dark and light areas showing up on other phals.

Any help gratefully accepted.
Norma