Vlad pool taking damage (not from DOT)

ok i have been seeing this for about a week now. i have been playing vlad and at times i would be taking damage and dying while in his pool. just played a game where i pooled and fizz dived above me and that killed me. no i wasn't ignited or taking DOT at times. cause his W wasn't up. i made sure of that before going in. i had about 1/5th of my hp then it just all disappeared after i was in my pool. this also happened when i played against a riven and even she called it that it shouldn't have hit me when she ultied over me and killed me while in pool. this only happens sometimes not all the time when that little mistake they did would've won me the fight but instead i'd die when i shouldn't be dying. would like this to be looked at please