Can you tie a loop in the rope below the subs? End result will be subs 8” or so deeper if you can’t get the loop out, if that is acceptable.
FWIW, we had Ed Brazil (RIP) and his diver Jay, survey and adjust our course about 10 years ago. Sounds like setup that you have. Ours is in 35’-40’ deep water. Some of the challenges: Like Deke says, some of the anchors really sunk into mud and were very tough to break free. Make sure the anchor lines are still in good condition (are they 23 years old or have they been replaced?) Breaking one, may mean losing the anchor under the mud. You may need to dive to each anchor and clip a fresh rope directly to the anchor (and work through the muck to do this). Ed had his “anchor wanker” to lift the anchors. It was a mini pontoon contraption, about the size of a single person fishing catamaran. Instead of a seat it had a hand cranked winch in the middle. The anchors would have been way to difficult to break free just by lifting.
BTW, with ours, if they were to be moved less than 6”, they tended to settle back in same hole in mud.