DIAGNOSIS That's hard water mineral deposit, and it usually means you're not using enough rinse aid or the rinse aid dispenser is empty. The 300 series is particularly sensitive to this for getting spot-free results.
FIX 1) Check and fill the rinse aid reservoir. It's the twist-cap compartment on the inside of the door. Use a Bosch-brand or high-quality rinse aid. 2) Turn the rinse aid dispenser dial to a higher setting (like 4 or 5). This releases more rinse aid per cycle. 3) Make sure you're using a good quality detergent pod or powder, not an old or clumpy one.
IF THAT DIDN'T WORK Your water might be extremely hard. You can try running a cleaning cycle with a dishwasher cleaner or a cup of white vinegar placed upright on the top rack. If the problem is chronic, you might need to install a whole-house water softener.
HEADS UP Avoid using extra detergent thinking it will help—it can make the filming worse. Also, ensure you're loading dishes so water can drain off them freely; nested bowls or cups facing upward will hold dirty water that then evaporates and leaves residue.