As long as you're able to operate the slide without huge difficulty and the gun is functioning normally I wouldn't go to a weaker spring. Chances are it will still loosen up a little more and even if it doesn't you really don't want to have issues with a carry weapon. Also, you say you've shot 50 rounds, I'm assuming that was a box of inexpensive "target" ammo. If you're carrying this, make sure you shoot it with the defensive ammo you are using, too. I know it's expensive stuff but you really don't want to find out the gun doesn't like the ammo you're carrying in it the hard way...also...you want to see where your defensive ammo is going to hit as it often will not be all that close to where the target stuff is.
John