Hello Jetphoto Community

Recently, I have severe problems with my Nikon D7100 and Nikkor 80-400mm 4.5 - 5.6 objective, in some light conditions creating dark halo around the aircraft. This is visible only when activating the function "check for dust" after uploading the photo. I use Lightroom for editing, taking care of not pushing up the darks too much.
I suspect that the objective is relatively old and might need a deep clean. What else can I do?


Photo as an example...