Very Poorly Guinea Pigs :(

As the title suggests, three of me Guinea pigs have been taken very poorly recently. Hex has been bleeding from his back passage, Vaniella has a hard round bump sort of thing near one of her nipples and poor Bella has been losing LOTS of weight. We went to the vets today, and I came out sobbing my eyes out. The vet thinks Bella has a very serious problem. She felt her tummy and told us that Bella has noticable swelling. It could be diabetes or a problem with her kidneys or liver. The first thing to do, would be to have a blood test and see if it is diabetes. They only need a tiny bit of blood for that. But if it's not... then we have a problem. They will have to do another blood test on her to find out whether she has kidney failture or someother kidney problem. Though they will need ALOT of blood for that. She is 600gms and they will need about 100gms of blood for that. Thats not going to happen. It's just WAY too much blood for her. And even if it were a problem with her kidneys, if she needs an operation, it's not very likely she will even survive due to how skinny she is. The average for her breed is about 800gm-1000gm+ so you can see how skinny she is -.- She eats and drinks like a monster, so I know she is haveing her fair share. <br><br>The vets say Vaniella's little ball on her belly is more likely a fatty ball. Which is very good news! But we have to keep an eye on it, because if it gets bigger or changes shape, then that will mean she will more then likely have to have it taken out. Which will cost, what? £300 - £400? Gah. We are just hoping it's just a fatty ball so we don't have to pay out money on it. Bella will cost a bomb with whatever she has, we are just hoping another bomb falls on us. Fingers cross for Vaniella! <br><br>Now we have Hex. The vet doesn't know what he has yet as his butt stopped bleeding once we got to the vets so she couldn't see what it was like. She says its much more likely to be bladder stones then anything else, but we will have to get a sample of the blood before she can make any conclusions. We have been keeping an eye on him too.<br><br>The money isn't a very big issue, we just want to do what is best for them all. We have moved the three of them indoors together as they lived outside with the other six Guineas so we can keep a better eye on them. We are weighing Bella weekly now, as the vet says she cannot get under 500gms. Does anyone now of anything I can give her to make her gain some pounds? Any advice is GREATLY apprecated! Thanks!