One of my cuttlefish had long-term scratches on her back which whitened if she was fed gamma-sterilised fish. If fed shrimp (frozen or live) they faded but never disappeared. She did lay a couple of immature eggs before senescence took hold.

Apart from the above I never noticed any sign of infection of wounds (including rear-end damage) in any cuttlefish.

The second time I tried to keep cuttlefish I ended up with one that was twice the size of the other (both small). We had to go away for a couple of days so I split the tank with some mesh on a frame & hoped for the best. When I returned there was a distinct "off-odour", the tank (6 cubic foot size) looked grey and I thought that everything was dead, but to my surprise the larger cuttlefish had survived (and continued to thrive!). The smaller cuttlebone floated to the top a few days later.
Marine creatures need much more reliable food supplies than fresh-water fish, especially fast-living cephalopods. I was apprehensive that they would not have survived even a couple of days without feeding.