OK, my take on this one is a little bit different.
I think an 8" standard plastic pot for baby/young jade is a little too deep -- especially with heavy commercial potting soil in it (it might be in a slightly better circumstances if you mom used cactus/succulent soil). My suspicion is that in the beginning, the jade divisions were doing fine because the surface drying out dried the interior of the pot nicely for the young roots, but when they started hitting the deeper portion of the pot where the soil had no chance to dry sufficiently, they started getting in trouble. Maintaining it in constantly moist condition the way you describe, the lower half of the pot is probably soggy all the time. I think the roots are rotting and dying in there and that's why the leaves are shriveling up. With an 8" pot though, letting it dry sufficiently through may dry the upper portions of the soil too much.
Oh, another thought -- with the good drainage you describe, the potting soil might have been a soilless mix. In which case, another issue might be that it's run out of nutrients. BUT don't fertilize just now.
My recommendation is to repot -- but not quite yet. I'd wait until the weather warms up at least until after last frost -- like tomato planting/corn sowing weather. (This might help: https://www.ghorganics.com/Phenology.html
) For now, water a bit less often -- definitely let the surface dry.
The way I would repot would be to turn everything out, mix old soil in 1:1:1 ratio with compost and sand and if you want to put them back all together again, then put them in an azalea pot/bulb pot (short and squat pots, same diameter is OK). 8" standard pot might be OK if it's clay. Individually potted, I wouldn't go smaller than 5" in clay though because small pots are a pain to keep from drying out. In plastic, 4" or 5" pot might be sufficient depending on the size of your plants. But keep in mind that Jade plants can get top heavy and plastic pots often tip over when the soil must be allowed to dry a bit.
HG does have a point about other pests -- mealy bugs and scale are notorious. So do check for those as well. I usually use cotton swab dipped in rubbing alcohol to pick them off.
to the right conclusion. My observation is that springtails seem to appear when overwatering is taking place. Fungus gnats are usually not too far behind.... 
Anyway Lisa's foliage moisture and AS's soil change and my humidity tray (where a pot should ALWAYS sit on gravel with free drainage).