Is this 1 plant? I see a plant on the left, and a long stem that looks different to the right, and then darker leaves below the 2 other plants. If the photo was clearer, I might be able to make out what they all are. I'm thinking this might not be a fern, and is actually Pedicularis canadensis. They are hemiparasitic and need host plants close by, so putting it by itself will cause it to decline. I could be way off.

I think it could be a struggling Japanese Painted Fern, Athyrium niponicum. Guess how I know what that looks like ☹️

Floral, maybe your climate is too mild, and they need a cold winter? I have a couple that are 20 years old, and still looking good.

They, and Ostrich ferns, are the only ferns that do well for me.

No, they do absolutely fine over here ... just not in my garden. I neglect it and it's not tough enough to battle it out with the thug plants. I see Aegopodium podagraria does well in your garden ... that's one of the few nightmares I don't yet have 😒

Swamped by Hellebores ....

Not Aegopodium floral, I would never grow that invasive thug in my gardens. It's native Sweet Cicely, Osmorhiza claytonii. They don't spread by rhizomes. They self seed, and are very welcome to do so.😁😏

Oops. Didn’t look carefully enough. To me Sweet Cicely refers to Myrrhis odorata.

@Jay 6a Chicago, as far as I can tell it's the same plant. Here are some more pics.

Here's the whole plant (the shadow at the bottom is me):

I'm pulling the plant section on the left to the side so that you can see inside a little bit, and use my finger for perspective:

Here you can see all 4 stems coming from the ground, less than 1" from one another:

I think that what you're seeing is the stem pointing upward is getting TOO much sun, the stem on the left getting a little less sun, and the stem on the right (the darker one) is getting the least sun.

Yep. The tall one is just a new frond unfurling this year.

A fern for sure. It's looking like a beat up Japanese Painted Fern. They take a long time to regenerate. I think it might do better with half a day sun, or dappled shade? The JPF in my photo is growing in a lot of shade. It looks ok there, but it doesn't spread, unfortunately. They are strong willed, and will hold on for years even when thugged out by more agressive plants. Just one of a few non native plants that I grow.

Thanks, @Jay 6a Chicago! I have 2 other Japanese painted ferns in my garden, one is big and beautiful but the other is fairly small and cutesy. I think I'll put this one near them and see what happens.

All the Japanese ferns I have the one that does the best is the one that gets the most sun. Its under an eave on the corner of my house and gets full morning sun and some bright but not direct afternoon sun. The others are under full shade and are alot smaller.