Ottawan,
I had some similar cases of just rooted happy figs.
One day they are happy (without a dome), and the next day the leaves just go limp.
A very bad sign - doing nothing is a one sure death sentence (for the twig)!
On close examination, the twig (wood) between the bottom roots and the
top leaves had rotted, breaking the 'plumbing' mechanism between the two, ( hence the wilting part).
I managed to salvage a few by:
(a) Very gently, taking off the plant from the potting medium, cutting off
the bottom rotted part, and repotting the top healthy part under a (vented) dome.
(b) Topping-up the potting medium around the top healthy part.
Using some structure, e.g., and inverted foam cup with the bottom-half-cut-off may help...
Again, provide a (vented) dome for added moisture.
The advantage of (a) is that the rotted part is removed, and it may stop any further rotting.
The down side is that the twig is disturbed.
The advantage of (b) is that the twig is NOT disturbed (some small root initials
may be just developing further up the twig).
If the original twig happenned to be a tip-cutting and new green
growth came from the very top - I have nothing to add.
However, if not, and the new growth is 'lateral'; try to 'up'
the potting medium to 'just-to-cover' that particular node.
I think that particular spot just happens to be where the most
veggie-activity is.
Either way, it is almost like starting over, with a limited chance for success.
I seem to prefer method (b). Good luck....