I'm sorry if this is an easy fix and I'm just not seeing it but I have 5 Jem/RG six-string guitars and from guitar to guitar the tension of the tremolo (ie, how hard it is to push down the tremolo) is different. In theory, since they are all six-string guitars strung up with the same brand of 9s and each using 3 springs in the same holes, they should have about the same amount of tension on the tremolo. One of my guitars is so bad. It's like there are 4 or 5 springs on the guitar. The only thing I could think of changing was springs but I didn't see much of a difference. Any insight into fixing this would be greatly appreciated.

In my experience not all springs feel the same. I have a 1988 540r with the original edge, and a 1991 540r with a low pro edge. One has 2 springs the other 3... They feel almost exactly the same... I think the low pro has a bit more mass, so maybe that is why it only needs 2 springs to feel the same. I think in your case It just depends on the springs. I have a js100 with a gotoh floyd trem and it feels super easy and it has 3 springs in an arrow shaped pattern. If your trems are all the same... The spring tension has to be it. I wonder if maybe Rich may be able to pin point if ibanez had different spring gauges used through out the years.

Springs fatigue and get soft, and not all bridges feel the same. Not all 5 of yours have the same bridge, even if you put new factory springs in all of them they'd still feel a little different.

I do agree, all the tremolos on all 5 of my Ibanez six-string guitars do feel different, however, there does seem to be an excessive amount of tension on the one in question. I did swap out the springs but I'll try it again with another set. All of my tremolos have 3 springs in the arrow-shaped pattern.