Yes . . . look at the primers on the rounds that didn't go "bang," and see if they have light primer strikes (this is quite apparent). If you have light strikes, and if you were shooting in the double action mode, just switch to Federal 150 primers and/or Federal ammo and you'll be good to go.
Back to the original question? The lighter spring is to lighten the trigger pull for competition use . . . and with use of Federal primers. Most, if not all players of the "gun game" crowd use Federal . . . and these guns are shot virtually double action all the time. Firing cocked, single action the hammer falls forward a longer distance and the primer strike is solid . . . even with lighter springs.
The standard S&W springs however . . . were chosen as being the best all-round spring rates one could use . . . to handle the great majority of uses of their products AND insure reliable ignition. Most people use their wheelguns to plink, target shoot and hunt in the single action mode. However, in the frantic yank and crank of a sudden self defense action, folks use double action . . . and ya gotta have "six for sure!"
Here's a wheelgun that's won a lot of matches for me through the years, a long-barrelled (originally) 25-2 in .45ACP. Both the double and single action trigger pulls are obscenely light . . . but totally reliable WITH Federal primers.
However, I wouldn't let my wife use this gun for self defense. As she says, "It goes off sometimes before I'm ready." It takes a lot of practice to shoot a gun this responsive well, while firing literally as fast as you can rotate the cylinder and get a perfect sight picture . . . but the results in a match are rewarding.
THEN AGAIN . . . this same gun could be ya in trouble if you weren't used to it and you were holding a robber at gunpoint . . . if someone sneezed and you jumped you'd shoot the guy.
Trust the S&W springs in your regular use S&W wheelguns. I sure do in most all my Smiths . . . and they are perfect for virtually all uses . . . and danged good too for "gun game" use!
T.