Bests & Worsts Reviews from Amazon

My 28# cockapoo has eaten these for quite a while -- almost daily basis; loved them and no problems. A couple weeks ago when I received the latest order, he had a couple and started having (TMI alert) loose poops that progressed to looser with blood and mucous. I wondered about the Greenies, but couldn't rule out anything else. Then, last week, it happened again. Greenies was the only thing introduced back into his diet on a regular basis. Without them, his gut recovers and is OK. Has anyone else experienced this?