Cassiopeia's Miasma W

Yesterday I played a game where I kept standing in a invisible pool of poison from Cassiopeia. It sucked! D: She had the Jade Fang Skin on if that matters.

I asked in /all chat if anyone could see it but no one really replied back and since I said that I felt like Cass kept throwing her W at me to mess with me.

I am wondering if anyone had a similar problem.