Usually, it’s equipment at fault in situations like that…less-than-ideal glass, not-so-great ISO performance.
But that’s not the problem here.
It could also be subject movement (ie. a shutter speed slower than 1/250th on moving objects).
But my guess is that your photos are most likely not quite focused spot-on (due to moving subjects or using the focus-recompose method of focusing or simply since you’re shooting wide open).
I would suggest exploring and experimenting with your focus settings. Maximize the focus technology that that camera has. I know for me, I’m used to shooting landscapes with a Canon 5Dii (which has very primitive focusing abilities) so I tend to not utilize the focusing technology when I pick up the 7dii for an event.