Faded white lines through iMac screen?

Hello, my imac is getting faded white vertical lines on the left and right of the screen. They are very feint but noticeable. I had this issue about 4- 5 months ago, and I took it to Best Buy where I bought it because it was still under their warranty. They sent it out and the screen was replaced and everything was fine until about a week ago. Is there a recall or something that Apple has put out with this issue?