Clearly hit baron with the ult. Looks like just weirdly delayed damage?
Q missing Baron and R missing Kha is because League has 3d graphics and 2d physics, and because you kinda shot in front of Baron's model. Barely, but just enough. He was leaning forward and his hitbox didn't move with him.
To explain that first bit - All hitboxes and collision in League are on a flat plane. There is no 3rd dimension in it for how it detects whether or not you're in bush, or whether something hits you. You are a circle moving across a square, and your Q is a smaller circle that originates from you and moves however far until it intersects with a circle that's designated as "can be hit by Ezreal's Q".
However, visuals - models and effects - are 3d. That's what causes the problem.
River is visually lower than lanes and jungle, but the entire map is mechanically flat. So it looks like your R hit Kha'Zix, but if your R and Q's visuals were matched to their actual positions, your R would have passed just to Kha's right and your Q went just in front of Baron.
This issue doesn't happen from river to river because it's all offset by the same amount, and there's no issue from land to land because there's no offset. There also should be no issue for something going from land>river>land, or any other instance where the conclusion matches the origin in elevation.