Not according to Hornady's 8th Edition, but Hogdgon who sells that powder does not show any load data for that powder in that weight 9x19, so it may not be suitable for that application. You mentioned two different problems I believe.
First the FNS, if it is new then yes the springs will be stiff until it is broken in. But I think your issue is a mag problem since you state you have no problem with the first two mags out of the three that come with the pistol. Check the mag lips on the third mag to see it they match the other two, they don't have to be off much to cause a feeding problem.
As to your wife's S&W Shield, It sounds like an extractor problem and may be dirty and needs cleaning. But I don't know for sure.
Jim