Karthus bug buff glitch?

So i am playing ranked as Karthus mid lane and i some times get a kill and get a buff either one i get but i started to noticed something when i died while i still had the buff with his passive and used my ult i get kill or a double or triple i spawn back in the game and i ended up having double buffs on and when i mean double i meant like two to three red buffs on that over laps and they don't go away but some time when the meter is run empty i am left with a red buff but dose nothing but just sit there and display, i even one time had two blue and two reds witch was a mind blow it mite just be my imagination but it happened not for sure if it is a glitch or not so some one look that up?