Too much light?

[SundayGardener]

Hello,

I recently noticed spotting on one of my "Aussie" Dendrobiums. I've attached a picture of the front and a picture of the back of the leaves in question, as well as a picture of leaves on other, shorter canes.

Is this sunburn, or too much exposure to light? Or something else? I had it sitting on a vase so that it was closer to T5HO lights, but have lowered it again.

As an aside, I seem to have a lot of spotting on an ongoing basis on all my Dendrobiums (which are all latouria types, except 2 Australian varieties from SVO, which have not been prone to spotting until this very recent development). I have been watering the latouria types daily all summer, but I think it is time to back off on that. Are dark spots normal for Dendrobiums? (I know they seem common on Oncidiums) If not, what should I be doing differently?

Thanks for any and all info and thoughts!