I'd say you have a winner with the ones that are surviving. They may just be a smaller tree, but with good fruit. If you have the room, why not give them a try and keep growing them?

Let's see. Zone 5B gets down to -10 to -15 degrees. Let us know if they stand up to those temps.

If they live would you be willing to trade for one of the plants?? I am in Virginia and would LOVE to have a pummelo tree.

DL

Citrus don't turn black and slimy in frost like some herbaceous plants do. Frosted areas simply stop growing. Leaves turn grey-green then brown and may shrivel up a bit and then just hang on to the dead branches.
Unless you happen to have put the plants somewhere protected from the worst of the cold, I doubt they'll survive your temperatures. I guess they just won't grow again in the spring.

citrange, that is true of some, but Keiffer lime will turn black as well as some others. and growth that is new or just coming out in a flush may turn black as well.

Pummelos are among the least cold-hardy of all citrus. We have difficulty keeping them alive even here in Lakeland Florida, where grapefruit thrive without a problem. Even big, established trees can die to the ground with just a moderate frost. So I suspect that with a few warm days, you'll find your plants are dead. I don't want to be a pessimist, but that's just a characteristic of the species.

In my experience pummelos are nearly as hardy as grapefruit. I have been able to grow them here in 9B for the past six or seven winters without serious damage. We just had a sharp freeze here in North Central Florida (first freeze of the winter at our house) and one of the pummelos was covered in bloom and new growth which was about four or five weeks old. The 27 degree temps left the blossoms untouched but the big, shiney new leaves are slowly curling up now and will eventually fall off.