Thanks guys, they are both definitely girls! First thing I checked when I got them
I've kept guineas in the past so I'm familiar with sexing them.
They're both on an excellent diet, lots and lots of veggies, fresh hay and quality pellet food. Neither seems fat so the little bulge Daisy has seems suspicious, but then again I would have thought if she was 4-5 weeks I'd really be able to tell, but it seems not. Here's a pic of her looking chubby:
I also wonder if perhaps she's less than 5 weeks.. maybe if she was put in another cage to give birth and then put back into the main pen? Can guinea pigs get pregnant while they are feeding babies? I know that after the first post-birth oestrus many animals are not fertile till their babies have weaned, but if she got pregnant later that would explain the smaller belly. Her last lot of babies might also not be 5 weeks as the rescue lady was just estimating.
Thanks for your help!
B