Is it a concern that 120v cables hang down from the ceiling in my crawl space?
You can run NM cable (the official term for Romex, which is a brand name) in a crawl space either ALONG the SIDES of the floor joists, or THROUGH them (i.e. fed through drilled holes). But you cannot just staple it TO the bottom of the joists. Since that may not be an option here, the next choice is to nail small "runner" boards to the bottoms of the joists, then staple the cable to those. The cable must be protected from being grabbed or pulled. But if those cables are now too short to do that and you need to replace them anyway, I would opt to drill and pull.