Federal Champion ammo from Walmart is well known to be loaded extremely light. My friend's Gen4 G19 works fine with it, when I'm shooting. But when she's shooting it, the brass barely clears and jams sometimes happen.
This isn't any issue, since she only shoots my reloads and Speer Gold Dots. But she asked for the "upgraded" spring, anyway, since it's a spare recoil spring for free. (And the gen4 recoil springs cost 3 times as much as the gen3 ones, so I'm not sure that getting double the life from them is a good deal!) If there's any real difference between the 03 and 04 spring, that difference is very subtle. They appear to be basically the same weight. The Fed stuff shoots basically the same as before.
There are also some reports that Glock has changed the ejector. If your ejector is thicker top to bottom than the older Glocks, it already has the newest ejector.
If you already have the 04 spring, I suggest you buy some NATO spec ammo. You can find it online for similar prices to Walmart FC. If that fixes the problem, then fine. If not, you can look into the ejector issue.