[GAMEPLAY] LeBlanc Doesn't Receive XP from Gromp?

I was planning on messing around with LeBlanc in the jungle in a custom game. I started on blue side and went straight to Gromp after buying a Hunter's Talisman, Refillable Potion, and a Warding Totem (Trinket). After an intense, 2v1 battle against Gromp (with the clone from my passive, "Mirror Image"), I finally managed to kill it; however, I received no XP and did not level up as anyone typically would after killing Gromp at level 1. The clone from Mirror Image died almost simultaneously with Gromp, but with a short replay of the incident, I noticed that, while my auto attacks were dealing 52 damage each on Gromp, it received 47 damage from what looks to be my clone's auto attack right before it dies (along with my clone).