Well, as in many of my experiences, I found out the hard way…tried to fix a sash by drilling a hole in the frame for a screw, and the glass began to turn. Noticed that many other windows were not as crystal-clear as they should be…tried to blame the wife for not cleaning the widows (painfully bad idea).
Well, when the windows were replaced, I took apart one of the sashes, and sure enough there was this coating which had turned cloudy. The window installer told me that our windows had metal particles sprayed onto the inside of the glass between the panes, maybe copper? I don’t remember. Anyway, it was to reflect sunlight back outside. He said the moisture reacts with the coating, especially for windows receiving direct sunlight. Apparently this is process is not unique to replacement windows
Now, my current house had a problem with one of the windows, but it never turned. I would guess, then, that not every manufacturer coats the glass. All I know is that once you get moisture between the glass panes, you're going to have to replace them. Nothing you can do in the field will restore them.