Yes as Quinn mentioned, quarantine is your only hope now
Try just a small tank like a 5gl with nothing in it except for maybe a small clay pot for a hiding spot(no worms or crabs can hide in clay). No current, just a single low running airstone will do. Use some water from your current system to ensure the same parameters. You could also bring the SG down, of course slowly over a few days.
I almost lost a yellow watchmen after it took a leep over the overflow, thank's to the polywool he didn't get blended up in the pump just 4ft below. It was 2 day's before I saw him as I was away for the weekend, and even though he was submerged he only had 2" of space between the overflow wall and the polywool. I put him in a system like above and after a week of rest and lot's of spirulina and garlic he was rite as rain.
That was about 3 years ago, ever since I use a piece of eggcrate wrapped in sceening material to cover the top of the overflow. It works great for keeping jumpers out as well as crawlers like snails and hermits
