IC Decoupling caps placement/routing
Did you know that vias add a few nH of parasitic inductance to your capacitor? Even the leads on body of the capacitor add inductance. Inductance is the enemy of decoupling, it is the reason why we use decoupling capacitors in the first place (so there is no voltage drop from the the wire from the voltage regulator).

So the less inductance you have the better decoupling you'll get, go find a PCB trace\via calculator and calculate the impedance of the capacitor. They look like the picture below. And if you add vias, the impedance dip gets worse as the cap filters high frequencies less.