Sorry, I can't say 100% for sure, but I have a couple of adult boys who talked me into way more yogies than usual one day last week and sure enough a day or two later we have lots of yellowish poop! I seriously cut down the yogie dosage since that one wild day! They don't have any symptoms or bad signs so I'm pretty confident that's what caused it. I'm keeping an eye on them to make sure they are playing, eating, and drinking to make sure the color goes back to "normal". Lulu and Lily are younger so I'm sure it would take less to affect their poop.