About the only thing that could cause it would be an insect pest. Turn one of the leaves over to see what might be hiding.

snails?

Thanks all - I checked again but didn't see anything on the leaves, stalks, or plants, but maybe I missed something. It looks like the same type of skeletonizing damage that Japanese beetles do to rose bushes. It's almost like the leaves are nearly dissolving at a uniform rate across the entire surface of the leaf... a very fine, evenly distributed skeletonization.

I'll see how the new leaves do after they unfurl and extend.

Hi
I grow only tropical lilies but have a similar problem.
Mostly in the spring just as the lilies break dormancy.
Can't find the cause but the lilies grow so fast by May the problem is gone lol I always suspected that it might be tapoles as I can't find an insect. This year for example have very few tadpoles and they show little damage .
Wouldn't worry too much aout it unless it goes into the heavy growing season gary