They have Botrytis (a fungus), it was probably spread onto your plants from the soil by water spray.

Dig up the top layer of dirt around the lilies and all fallen leaves. dispose of in the trash. Hopefully they have enough foliage left that they can still feed the bulb. If not the bulb will probably still send up a plant next year, but it may be smaller as the bulb will have diminished in size since it was not fortified by the leaves over the growing season.

Lilies don't need to be watered much. (Every other day is a lot even in dry conditions.) If you must water, use a watering can so that the water doesn't spray up on the plant. You can also use a soaker hose as long as it is covered in mulch so the mist doesn't come up onto the plant.

Good Luck!

-Helen

Here is a link that might be useful: Botrytis link

Thank you Helen. Should I spray the survivors with anything for that? Also do you recommend removing the mulch around them as well as the soil?

Search Botrytis on the forum (and on Google). It's a real problem for a number of plants because it can move pretty quickly. I believe its common name is "fire blight". I remember passing along the advice to use rose fungal spray that I read somewhere, but I haven't used it myself.

I'd remove the mulch as well (the fungus must be on it since your plants have been affected) and it can get kicked up by rain even if you're careful with watering.

-Helen