Very nice, looks like Carnosa, Sorry I don't recognize the problem. Is there something applied to the leaves that's making them so shiny? Could it be related to that?

You are correct; it's sun damage. Some Hoyas can handle a western exposure and others can't. It's hard to predict because some of the species that can handle western light have much more delicate looking leaves than carnosa. I had my diversifolia growing in a west window all winter and it loved it, but in the spring I had to move it because it started to suffer.

If you pull your blinds in the afternoon, as you've been doing, I don't think you will have any more problems. My leaves look exactly the same when they get too close to the grow lights.

I don't do anything with the leaves to get them shiny, I just mist it with distilled water occasionally (our tap water will leave minerals on the leaves.)

I'll make sure to protect it from too much light, plus I suspect the extreme heat hasn't helped: It's in an room without a/c, and last week it was around 110 or more every day.