Something poked it.
Unfortunately, it looks like the tweeter used in your speakers is aluminium and not a soft dome.
Like with most dome tweeters, you can try to gently pop the tweeter back out using tape which does not leave a residue. Unlike with soft dome tweeters, however, metal-based tweeters are not very resilient to dents in that even after you pop the tweeter back out there will still be slight, potentially barely perceptible, creases in the metal.
From past experience, I will tell you that it is impossible to return a partially dented metal tweeter to a perfect pre-accident state. This is not to say that the tweeter won't improve significantly after the "tape" repair, it very well may, but if you are like me, "close enough" may not satisfy you.
Before messing with the tweeter further, it may be worth it to contact Def Tech and ask them if they will send you a new tweeter. Dome tweeters generally aren't a very expensive part, and when I asked the same thing of Mirage when one of my tweeters was dented, they sent one out right away.
In the case of Mirage, they sent me the entire tweeter assembly, and the repair required nothing more than a hex wrench and ten minutes of my time.