the weird annie ult glitch

When I played as Annie in a normal draft, I had my ult and it was a fine. But when Tibber died, my cooldown was cut to 17 seconds even though it was suppose to be 65, I didn't have the blue buff or anything that has cooldown reduction. after 5 ults or so in like 1 to 2 min, it went back to its originated cooldown. RIOT, plz fix