Granite stain from fake flowers

Hi to all and thank you in advance for your replies.

My family and I have a big problem. A very dear family member has passed away and about 4 months ago we bought a memorial stone made of granite. Over the holidays my mother for the first time placed a set of fake flowers in the person's memory and a few days later our granite was stained red. We walked all over the cemetery and although many stones had fake flowers ours was the only one stained. Does anyone know what can cause this to happen? Do we have a defective piece of granite? I don't know much about granite but is there a sealer or some sort of protective cover that was not originally put on our piece?

Thank you again.