Matthew - I am new to RealBakingWithRose, but have a bit of experience with similar issues. If your utensils are holding on to odors from the foods that they contact, then that is more of an issue with the composition of the utensil; I love the suggestion of denture cleaner for this, but soaking in plain baking soda slurry should also work as well. Pinpointing the problem from here takes a little bit of problem solving. Are any other items coming out of the washer dirty, spotted or with a film? Does your water have a high calcium or magnesium content? Is there a white scale on the inside washer surfaces? When you put your head into the washer when its empty do you smell an old dishwater odors?
Detergent brands have subtle differences, some work better with a particular supply water quality. Rinsing agents make up for some of this, but rarely is the detergent brand the reason for unclean items, however. Odors & flavors that resemble dirty dishwater originate from retaining dirty dishwater on or in the item. I understand that your spatulas are about 10 yrs old, but I don’t remember if you described the composition of the spatula head, the handle, or if they are molded (1 piece) or come apart. Spatulas that separate from the handle will retain dirty odors within the mortise that the handle fits into. Because the majority of our “taste” resides in our smell ability, we will taste odors that we smell. Removing the spatula from the handle, scrubbing and deodorizing may correct this depending on the material composition.
If these are not the issues or, as previously described, it continues to happen with new utensils, the problem is within the cabinet of the washer or with the rinse cycles. The first step I would perform is a thorough cleaning of the washer (Yes, dishwashers have to be manually cleaned periodically! I do this every 1-2 months). Any decent kitchen spray cleaner that degreases & disinfects will work for 1-3. 1. Clean the filter tray: remove all debris & sludge, wipe down with cleaner. 2. Clean the door seal: the seal that makes the door water tight has folds that trap food & slime. Clean within each of these folds along the entire length with the cleaner & dry with a paper towel. 3. With the door fully open, clean the space of the cabinet that the very bottom of the door covers up. 4. Run an empty hot cycle with a “dishwasher cleaner” solution that cleans & disinfects. You can find these in the grocery isle with dishwasher detergent. You will put the bottle upside down on the bottom rack & run on the hottest cycle your washer has (read the directions, DO NOT remove the cap. a wax plug will melt and empty the caustic cleaner during the wash cycle). 5. Inspect the bottom & top water sprayers: look into the little holes for debris. If you see crud, remove the sprayers and clean. I have used toothpicks and high flow hot water to flush the sprayers in the sink of older washers.
Use the washer for a week and see if the problem resolves. If you have odors still then there may siphoning of dirty water back into the cabinet during the rinse cycles. I can describe how to check for this if needed.
Let me know if this helps!