Double Hung Windows and Spring Repair

I have wood, double hing windows throughout my house. When I went to open windows yesterday, several springs came lose in several of the windows. There is a small, plastic clip left in the bottom of the plastic guide on the side. There is a plastic piece on the bottom of the spring, now sitting way up in the guide. How do you repair this? How do you get the window apart to get at this? Do you have to buy whole new spring parts? In one window, both springs came loose so the window won't stay open unless I use the old board prop-up trick. In others, only one spring came loose.

Does anyone have any idea why this suddenly started happening?

Thanks.

 

<Does anyone have any idea why this suddenly started happening?>
Because its your turn.
To remove, raise enough to grab at the top and bottom and slide sideways to release from the other channel.
Do the clip at the bottom and the piece attached to the spring appear to have been one part, broken?