The same is happening here to I'm gonna email Randy, bet he will know.

I really don't know what's going on here. My only guess was sunburn. I've seen that on my plant in the past. However I looked at some leaves of my plant where it climbed onto the roof and got full sun during some 90 degree weather. They look burned, but not like the leaves on Pat's plant.

Randy

Randy, I moved it in a bigger pot and it started to grow about 2 inches and put out new leaves so today I cut the old ones. I looked with a magnifying glass on the leaves I cut and I could not see pests. I am curious to see if this will appear on the new leaves. Actually I keep my fingers crossed not to happened to the new ones. I'll let you know.

Pat

Sunburn I think. Young membranacea leaves are very delicate and if the root system is not adequate the leaves will get scorched so keep the cuttings outside well watered in full shade.
Myles

Here is a link that might be useful: P. Membranacea

Mine is also very sensitive to wind. Another thing might be you are either under or over watering it.