Freelander 1 harman kardon

I have the harman kardon system with the becker sat nav in my freelander 1 face-lift. The front passenger side tweeter and large door speaker are working fine, the driver side front, passenger and driver side rear large door speakers are working but very quietly, the tweeters are also working but I couldn't be 100% sure if they are running quiet or not, My audio and electrical skills are my weak point and I have reached the limit of said skills. I have cleaned all speaker connections, tested the ohms of all four of the large speakers with a multimeter and the all come back exactly the same. I have checked and cleaned the plug on the amp, had the head unit out checked, cleaned and made sure all plugs are secure. I'm not really into my audio so not worried about having the latest double din android set up with 1k Watts of sound, I'm happy to replace things if need be just don't want to start throwing cash at it unnecessarily. I have done a search but haven't found anything that has helped. Any suggestions an audio incompetent can try will be great

Speakers are know to fail internally because of rust in the pole piece around the coil.
Try gently pressing on the cone, and see if it's free to move, or is all crunchy sounding.

Externally they look great but I will try to gently moving the cones, who knows what's going on inside.
Thanks for the suggestion