Yamaha experts needed. Purple logo lacquer

Hello guys. I was wondering if anyone could help me with some lacquer maintenance questions. I have a seen for some reasons on Yamahas from the 70'-80s (purple label 62 altos and sopranos in mind) that they tend to end up with a multiple red rot lacquer spots some even develop black spots from the zinc..Is there any way to prevent that? I have 62's and I can already see changes in the lacquer that is going towards there. I've searches online and lots of yamaha tend to age badly like that. Ive attached photo. Look closely the alto bell in the first 3 pics you can already see light black ish spots..what is that? Also the last pic, look on the keys the tiny red spots..same question..How do I prevent and stop both condition from getting worse? Thanks!!!