Elipsa SE's Tweeter Surrounding material not aging well

[esteban]

My Elipsa SE's (or "Reds") are almost exactly 5 years old. They still sound great. But lately, I noticed that the material used on and around the tweeter area (right around the "sonus faber" etched logo) is showing signs of what I could only describe as "aging". This is a rubbery, soft material. I do not know its name nor exact composition. The tweeters themselves sound perfectly fine and nothing seems to be affected sound-wise, but visually there is a faint, minor discoloration around this area and the material is becoming slightly "sticky" to the touch. I tried cleaning this but I only made it worse, so I just let it be.

I tried taking photos, but it's really hard to capture. It is minor, but noticeable only from up close and when touching the surface area immediately around the ring radiator tweeter.

Is this normal? In my experience, most of these rubbery / soft materials used in so many other products tend to get sticky and eventually start to disintegrate. Should I be worried?