Caused diarrhea in my guinea pigs

My pigs loved this but then had reddish diarrhea the next day. I threw it away. I thought it was coincidence but then I bought a new one a few months later and same thing happened. I’m Not sure if it’s an ingredient in the dye but this never happened to them when they were younger pigs. I used to get this tunnel for them all the time and I never came across any diarrhea.

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