So my two guinea pigs, Chocolate and Powder are birth sisters and has always lived with eachother,They have always been bonded with eachother, and powder is more shy and chocolate is more bonded with me. they have never had any problems but as they have grown older (they are like 4 1/2) they have been not getting along, i recently upgraded my c and c cage and got another hut because they cant stand being in the same hut together. they dont really fight over food. when they get their veggies they stay far away from eachother. but i just want to know why they are acting like this and how to prevent it? Thank you!