Granular suggest sediment got into the system or possibly the anode rod. Atwood does not have one.
Is the stuff clogging arerators white in color? If so it is lime, magnesium etc.
Even with filters lime in solution will get though. Lime in suspension will be caught in many filters and it will gather some, of the lime in solution, out, of the water.
You didn't say if you always use a water filter.
A water softener will take lime etc out but you still need a filter before it.
Lime and sediment will cause plenty of water heater problems.
First water heater, in our old home, had perhaps two hundred pounds of lime in the bottom when we changed it out. Had to replace several heating elements that lime coated and caused failure. It is well water. A filter solved the sediment and some, of the lime problem. Water tasted excellent though and several Folks came to just get our water.