I always look for pellets with the highest vitamin c content. Those which I have found to have the highest are the excell range (they love the black current and oregano ones these are also smaller pellets too) there is the mint ones which are a larger pellet and the little one seems to chew these in two or three bites. Excell have around 800mg/Kg of vit C I think, Harrington’s, although loved in the past by my previous guinea pigs, only have about 300mg/Kg. And you only want to feed them around 50g per piggy per day once 6 months old.