The only one I didn't see practice was Chris so I have no idea how he did - although if his last 2 performances are anything to go by, he'll be in the bottom 3 again.
From the ones I saw practicing, I'd say Gina was by far the worst. Nick wasn't very good with his singing but I've got a feeling he'll pull it off with a comic performance.
The other one who didn't sound too good IMO, was Dawn although I think it may have been because I just heard her singing with the piano - she'll probably sound a lot better with the full backing track.