[GAMEPLAY] Enemy getting execute even that I just damaged him

Dear Riot. I was playing Shyvana top. Zed dived my tower. I hit him with my E just before I died. He died about two seconds after that, and still got executed. After that, in the same game, Kindred dived me too, and I hit her with my E. She got executed too. I'm playing on EU West and my ping was 49ms, so I think that It's not possible that my E would have not hit even though I saw it hit. It even left the mark on them, and the mark was still visible when they died. I'm not sure if that happen every time, haven't tested it more, but as I was dived two times in the whole game and it happened on both of those, I'm pretty sure it happens every time. About my items, I had Tiamat in the first appearance and Titanic Hydra on the second. Zed had Yomumu's, Kindreds items I don't remember.. Sadly I don't have pictures or anything since that happened so fast that I wasn't fast enough to take video or picture about it. I hope this will get fixed as soon as possible