Piggie died at nearly 4 months

Question
I recently got two piggies, Coco and Chanel, and have been feeding them fine, and they both seemed perfectly healthy, until today. I saw them in the morning and they were both okay, but when i came home about 7 hours later, one of them was dead. There was nothing wrong with her, I though she was actually the healthier of the two, but apparently not. The other one is fine, and I can't think of anything that was wrong, because she was in the greenhouse, and it was fairly warm in there but not that bad, and the other one was fine. I recently put a salt lick in there too. What have I done wrong and why did she die?? I need to know because I am getting a replacement for the other one (She is still very young and needs a friend) and i don't want to do anything wrong again! Please!

Answer
hmmm, well firstly guinea pigs like all rodents are good very good in fact at hiding illness and so some illness is still the most likly, but guinea pigs do not take well to heat, heat stroke is a very common cause of death so in summer months i would keep them out of the greenhouse. really the other would be best suited going to a vet but a few things you can do yourself is check for the following.

make sure there is no cloudyness/gunk around or in the eyes. check there is no hair loss, check that there head is upright, ie not leaning to one side like a dog when he is thinking. they are still moving around fine, still drinking and not sort of jumping as if someone suddenly shouted.

est of luck with the other guinea and etting him a new friend