Q.Hostas
My hostas have a silvery color on top, not a powder, and look as though they have a yellowish color wet spot on them. But they do not feel moist. I have snails but I am treating that problem and the color is not snail mucus on the leaves. They have never done this before. Some of the leaves have a small brown dot on them but not too many
These articles may help you identify whatever is ailing your hostas:
https://www.gardeningknowhow.com/ornamental/foliage/hosta/hosta-problems.htm
and
https://www.gardeningknowhow.com/ornamental/foliage/hosta/hosta-plant-diseases.htm