I spent a year with a pair of Martin Logan Motion 40's... the model below the 60's. I purchased them used so they were fully broken-in. Bright is not a word I would use to describe them. Sweet and airy is how I would describe the Folded Motion Tweeter. I sold them and still regret letting them go.
In my opinion they need more time. The manual with my 40's said to break-in @ 92dB for many hours if not days... I forget exactly the time specified. Personally I would not play them that loud but a longer break-in could be the key. As someone else mentioned, play them constantly at normal levels for a week or two or three. Or until the return window is near. Many days of playing time also made a huge difference in a pair of speakers I got with aluminum dome tweeters. And check for any issues upstream.