Elixir of Skills bug

I was just playing a game where I had and I hit level 18 in the 50 minute long game. The thing is, that you can't level up a skill due to at level 18, the marks to pick which skill you level up are grayed out and will never go away. You feel like you should be able to level up a skill, but by then all of your skills have been ranked up and the game is confused. So this should probably be take care of. I'm not sure how many other people have seen this happen, but I just did while playing my new favorite support