are the negatives of underexposed prints salvageable?

Hi,

Firstly, I'm a total amateur.

I used 800 Fuji Press for the first time because I bought a long zoom
for a Volga trip. I sent 12 rolls to a local lab for developing and the
prints are awful - totally dark. The balance of the rolls I sent to a
Fuji lab and they came out fine.

Is there any way of ascertaining whether the negatives of the
underexposed prints can be re-done successfully?

Thanks,
Bonnie