Anna, that 58deg. might be cool enough to keep them growing slowly, but as soon as they start putting out leaves again, I'd think you'll need to pot them up individually. If leaves are growing, then so are the roots and yes, you will have a real mess next spring if you let them work on strangling each other all winter.
For now you might get away with leaving two or 3 of them in that tub, and potting the others in something like a plastic storage box. Or put a couple in a large pot, and put them where the greenhouse is coolest to keep them dormant?
