Correct. You have a seal failure in the glass unit. You'll need to identify the manufacturer if you want have it covered under warranty, otherwise a local glass shop can get a new IGU for you at a reasonable cost.

HomeSealed already answered you so this is a bit of an echo.

Failed sealed allow moisture to enter = condensation and failed low-e in most cases. Sometimes we see just bad low-e but this looks more like moisture related.

Is that a picture or operable unit?

Look for manufacturer's labels on the operable units and see if you can track it down that way.

It is an operable unit. We took the whole unit out and have examined every inch of it and can't find any label! I guess I'll have to call a glass shop.

Look in the head jamb and on the sides of the sashes. Search other windows that were replaced at the same time. Sometimes the label falls off a particular unit so you can search for days and not find it.

Have you looked through any paperwork the previous owner may have left with the house?
Contact the previous owner and ask where the windows came from, do not complain to them, just ask for their help.

theWindowNerd...

They didn't leave any paperwork on the windows, so I just sent an email to the owner asking for more info.

Check the other windows or take a picture from further back and I can tell you where to look.

Windowsonwashington - here is a picture of the window taken from farther back

Its a 2-Lite slider.

You need to lift one of the windows up and out of the track and look on the rails of the window (top and bottom) as well as where the window shuts into for the sticker.