No damage on Xerath Q

I was playing a match just now. Every once in a while, I would use my Q to poke. About half the time, during laning phase, my opponent very clearly should have been hit by my Q, but didn't take any damage. Later in the match, while pushing a lane, I hit all the minions with my Q, my Rylai's slowed them down, but they did not take damage.

Is this a problem anyone else has noticed?