So you're only having this problem on slap shots, not snap shots? Normally I'd say that since you were going from somewhat of a mid-toe curve (Sakic) to a heel curve (Getzlaf) that you might be shooting with the puck starting in the mid-toe area, while heel curves require you to shoot from the mid-heel area, but that's something I'd expect you to notice more on snap/wrist shots, as slap shots with open heel wedges like the Getzlaf tend to be pretty forgiving in terms of where you strike the puck. Still, trying to make sure you're striking the puck in the mid-heel area, not closer to the toe.
Agreed with secretsquirrel that you should make sure you aren't opening up the face of the blade when shooting, keep it closed, let the loft built into the blade and the flex of the stick get the puck up.
One other tip would be to hit the ice just slightly with the toe first, like this:
Your blade ends up flat on the ice anyways, but I find it gets my wrists in position to automatically roll/snap at the end of the shot. With wrist and snap shots is easy to build that roll/snap into your shots, with slappers I find it tougher to time properly unless I strike as in the video above, slightly toe first. Don't go overboard with it, your blade is almost flat when striking the ice, the toe hits only just slightly first. Once you get the hang of it, I find this style is great for shooting low, hard, accurate slappers. If I want to shoot high I strike more mid blade first, not sure if that's proper technique or not, just what I do.
Finally, is the blade of your stick still stiff? Soft blades can throw off my shots, just put your thumb in the middle of the blade, grab the toe with your fingers, and try to flex it, if it flexes easily your blade may have gone soft.