Selecting correct spiral balance for tilt windows

I purchased 4 red tipped S600's as that is what my tilt window has...but I wonder if I should have purchased black tipped instead? The window sash weighs about 45lbs. The windows were never easy to open and close, but they got to a point where they wouldn't budge. I watched the videos and installed 4 new balances but still can't seem to get the window to open and close properly. Should I keep the red tips and just apply more tension or would the black tips be better? By the way, I also replaced the pivot shoes. Thanks!

I guess I should also add that the S600s are 28" for the bottom window, and that the window sash is 49" wide by 29" tall, double paned, and aluminum. I just took it out of the frame again to weigh and it clocks in at 41lbs.

Again, the original balances were red tipped and 2 on a side.

The top windows are the same size and have 26" balances installed, but the top windows are another project for another day as we rarely ever pull them down and open them!

Thanks again!
John