Salt dispensers are found on machines with built-in automatic water softening. A number of brands make models with this feature.

Water chemistry could have changed in your area, but that's usually a seasonal thing, so it's likely you should have seen a similar issue last year at this time. You can get a report from your municipality as well as comments on whether anything has changed lately.

I feel like I should know the explanation for what you're seeing as I'm so confident I've come across it before. But right now I'm drawing a blank. You could try running some vinegar through the next few loads to see if it helps to at least clean out your dishwasher.

Have you noticed any difference based on what else you stack in the machine at the same time? Try not putting anything metallic at all into the next load.

Have you looked carefully at the package of detergent to see if its chemistry has changed since previous packages you may have bought? Phosphate versus phosphate free for instance?

Does you machine have any similar chalky or scale buildup? Around the heating element (if it's visible in your model), spray arms, etc.. Removed and/or cleaned the filter yet?