Karen it looks like possibly cold damage. What conditions has the plant been in?
Bryan

All my dyckias and hechtias spend winters inside a cool garage under lights, starting when nighttime temps begin to dip below 40. The minimum temp in the garage during winter is 40 degrees, and they get minimal watering while inside. We have plenty of warm spells during winter here in NC and I open the garage door to improve the air circulation whenever it gets above 50 degrees. The rest of the year they're outdoors with sun until about mid-afternoon and then dappled shade the rest of the day. They get regular water during the growing season.

I haven't seen anything like it on any of the others, but the new growth on this one is affected as well as the old. Despite the appearance of the foliage, this one bloomed this past winter in the garage.

Karen try taking plant out of pot and rinse the soil off the plant repot in new pot and add a little osmocote. I had a few like that and this seem to help. I am not sure if its cold related or some type of fungus. I use half pro mix and half soil conditioner.
Bryan

Bryan, I need to pot up a few others so I'll do this one too. I hope it helps. It's really been bothering me to not know what this is.

The best way to check to see if it's a fungus that's causing the problem, is to buy or borrow a small magnifying glass.
If you look at the spots on the top of the leaf and underneath, you'll see small dark brown or black dots, these are the fruiting bodies that spread the spores.
Ideally, you should cut off all affected foliage and burn it.
The disease is spread by water falling on the leaves.

That's a good idea -- I should have thought of it before. I have access to a dissecting microscope and can look at it under there. Unfortunately the entire plant is affected, so if it turns out to be fungal it would have to be destroyed if I can't treat it systemically.