HELP!

So I know I should have taken a picture of it, but alas, I did not. I think my garden is being taken over by some kind of mold/mildew. I have been Googling all morning to find out what it is, and I can't! I noticed it first in the cucumber bin. I noticed that the soil was starting to look like it had ashes in it, kind of like the big pieces of mulch had white rims around the sides. And the plant itself is kind of yellow now. I went to water today and found that it looks like it's in all the containers. WHAT DO I DO???