Should You Remove Old Mulch Before You Reapply?

Question

Some of old mulch has mildew.

Answer 1

The mulch with mildew you can remove, but leave the rest of the mulch, fluff it with a rake, and add enough mulch to bring it up to about 3 inches.

https://www.gardeningknowhow.com/garden-how-to/mulch/should-you-replace-mulch.htm