Beyond making sure there isn't some grit in there impeding motion (unlikely if two 15x magazines both top off at 12 rounds exactly) there isn't much you can do.
Think about it, that spring tension is an important part of how the gun functions ... why would you try to reduce it? Load with a tool, don't force anything past a hard stop, you'll know when the follower bottoms out, leaving you with about half a round's width of space (that's room for the feed boss when you insert a full mag into the gun) ... unless you're hitting that definite hard stop the mags aren't full, and you couldn't be hitting that stop unless you has mis-matched followers/floorplates or something (I don't know the P95's mags all that well, but sometimes 15x mags will be nerfed for CA/NY by using a taller follower - or an insert in the bottom - or divots in the mag body to prevent the follower from going all the way down)