Black spots inside Cattleya leaf

[Skycat]

Last night when I went to bed, my grow light happened to be shining on the Catt in such a way that it showed this (which only shows up decently in a photo if I DON'T use the flash). With the light from the grow bulb, you can see through the leaf.



What's concerning me is the fact that this stuff seems to be inside the leaf, and I have no idea how long it's even been like that.

It's in the other leaf on this pbulb, too. The other leaf has a huge blotch at the base which is clearly on the outside, but it's been there since I got the plant and hasn't spread, so I haven't been worried about that bit.



Here's how the leaf in the first pic looks with the flash on; you can only see the outside of the leaf this way.



This is one of the older growths, too. The newer ones seem fine, and the plant has recently started making a new growth. Is this a thing that happens to old Catt leaves, or is it something I should worry about?