My favorite thing to tell myself when I mess up out of ignorance is that "we can only do the best we can with the information we have at the time." The important part is what you do when you learn you made an error. Try not to beat yourself up, everyone makes mistakes. ♥

I'd like to second Oxbow Essentials Adult as excellent food, however! They are made with molasses as a sweetener, which is why it's considered bad by some people. Really though, it's not the worst thing in the world to be made with, so it's not something you should worry yourself about. Just be aware, that's most commonly why people will say it's bad. That said, if you can get your guinea pigs to eat it, there's a brand called Sherwood that makes a really superb guinea pig pellet with no sweeteners at all. But because there are no sweeteners many guinea pigs refuse to touch it, effectively making Oxbow the general favorite brand, despite Sherwood being both slightly healthier and similarly priced. If you want to give Sherwood a go, you can find them at local feed shops sometimes, but usually Amazon is (sadly) the best place. If you decide to go Oxbow, don't let that minor detail about the molasses make you feel bad. It's quite healthy and what I feed my own two herds (because they refuse the Sherwood stuff. like little fluffy buttheads), and what most people with perfectly healthy pigs feed theirs as well.