Chane replacements x 6

It sounds like your existing balances are either too short or too strong. Before I suggest anything, can you verify that the length of the metal channel is 33"? I'd also like you to tell me the precise weight of the sash and the height of its visible glass. That data will allow me to verify the appropriate size and spring calibration. 

The sash is the square glass panel that the balances support. You might think of it as the window itself, but in the industry it's called a sash; the "window" is in actuality the entire installation, frame and all. We use these terms to avoid confusion.

You can weigh the sash by removing it and placing it on a scale. Any common bathroom scale will do.

As for the visible glass, it's exactly what it sounds like: it's the glass that you see for the sash in question. You don't measure the vinyl or anything else, just the glass.