If it was me, I'd pull it and keep it in a 10 gallon tank. 100% new water aged 24 hours, aerated. No meds, unless by end of day 2 it still isn't recovered. I would also give it more light, and up the flow. I'm guessing, the water quality isn't helping it recover, that's why I'd move it asap. Then I'd also guess the light isn't enough par/proper spectrum. Higher flow is better than lower flow. When it looks like that so far into it, time isn't on it's side. I would act sooner than later. IMO, those clowns are too big for a new anemone like that to recover, even a month away I wouldn't put them together. It needs to be MUCH more healthy before it will put up with them. Best of luck to you, I hope you're able to get it to pull though. They can be very slow to recover, but the flip side is they can go down so fast.
What is the par at the location you placed it? In my tanks, they do really well in the 1000-1500+, the higher the better. That's one more reason everyone suggested first placing it so high up, best light and flow is up high in the tank.
Are you feeding it? If so, what, how often, how much, etc? Not suggesting it, just a detail left out...
Details matter, there are so many details, and they all matter. So often details are left out. Accurate guidance is difficult to give with lack of details. The more details, the better help you may receive.
Everyone can do this:
Gig in trouble??? GIVE IT A "RESET"...
(you can do this over and over, I have, it works)
Put it into a 10 gallon tank, as if you were treating it, but don't use meds. Change water every 24 hours, aged 24 hour salt water, aerated. Make new water at the same time everyday, the same way. This saltwater will have properties of XYZ at every 24 hour interval. This is different than saltwater that is a week old, or 2 hours after making it. I look in my bucket after a week, things precipitate out of the water. Just look at it, you don't even need to test it to see there's a build up in the NSW bucket! This is precipitation that hasn't occurred after 24 hours, but does occur after days or weeks of being made and sitting. Things in the water react and have a value of XYZ. GET YOUR GIG USED TO THIS WATER VALUE, in the 24-48 hour window of the age of the water, then change it and repeat. It will be difficult, unless you're a pro (and I'm not) and have excellent water quality. Using and encouraging others to use your DT water in rehabbing and treating anemones is only setting others up for failure.
Once you get your water to be a "nonissue", get the flow and lighting figured out.