Howdy Chris:
You might have some calcification deposits, which are gritty and sand like. They can be desolved by soaking in vinegar overnight. Then follow with a thorough cleaning and air preasure drying. You may need to use a welder's tip cleaner to get into the smallest holes to poke them clean.
If you don't get all of the grit out, it will come back to haunt you.
Adios, David