Need picture.

Those look like big, healthy plants that have outgrown their containers. They would be much happier in the ground. Do those buckets have drainage holes? If not, that would account for the wilting.

Also it is never a good idea to spray or use any kind of pesticide unless or until you know exactly what you are treating for. Brown spots on leaves do not automatically translate to a fungal issue. Applying a pesticide when just guessing about the need could lead to other, far more serious issues than what you are hoping to resolve.

There are drainage holes. A bunch. And the potting soil is one that makes sure it doesn’t get under or over watered.

Everything I read and asked about said fungal. Oy. Hope we didn’t mess it up

Are you planning to eventually plant them in the ground? If not you may want to thin them and grow one plant per pot. Sun flowers get large and their roots need room to spread.

All your plants would do much better in the ground. What was the rationale for keeping them in containers?

What Roselee said, that's way too many sunflowers in each bucket.

I see that Houzz is sorting our posts starting with the newest. That makes things hard to follow sometimes. If changed back to "Sort by: Oldest" it seems to stay that way on subsequent posts.

If you access the site via Garden Web and not Houzz, everything remains in chronological order from the oldest to the newest/

The ground wasnt an option :(. And we just kind of put seeds hoping something would catch... and then they all did.