One last ditch effort before the snip could be shaking out the soil and re-potting in fresh mix. I've never seen HLV either so I don't know how it manifest itself.
Right now I'm letting the cup dry out and this might be a good move. Can't hurt...
I'll carefully dissect the roots and soil in an effort to find the culprit I suspect most; root aphids. If I don't find any then I'm leaning towards some kind of virus.
If I can't diagnose the problem, it gets shit canned. If I CAN diagnose the problem, then either I treat it or shit can it.
The strain is "Madara" and I planted all 4 beans in the pack. Three are fine, they're on the left in the pic. This one hasn't been right since seedling stage and it keeps getting worse rather than better.