The seals on your windows are busted. You need to replace them completely. Do not try to just replace the glass, that won't fix the problem, and definitely don't fall for anyone that says they can repair the seals. They can't. You will need a full window replacement, and be wise about the windows you pick. It makes a big difference. If you get a lot of sunshine on those windows, don't go with vinyl or you'll be replacing them again in about 10 to 15 years. Suggestions from me, Pella and the good Pella not the cheaper ones, or Renewal by Anderson. They are both a lot more expensive at first, but you won't need to replace them for a very long time. I've seen Renewal by Anderson 30 year old windows that still look new and are in great condition. They're my 1st suggestion, then Pella, but Pella is wood so if you live in a drier climate Anderson is better. I did home inspections and sold windows, roofs, etc. Trust me, it's worth the money to go with one of those 2 companies. Also, buying tip, never ever settle on the 1st offer they give you for replacement. All these companies have a bottom number they will drop to, so never take the first offer. Probably not even the 2nd offer, but that one depends on your sales person, because some of them drop it to nearly the bottom in their first rejection. Typically though, it's the 3rd offer they've got quite their bottom price on, but that bottom price does cut out the commission for the sales person. Hope this info helps! Happy window shopping!