Hi, my name is Renae and I'm an appliance repair tech. Does your washing machine leave black or brown flecks or greasy or oily spots on your clothes? You only need to use two tablespoons of detergent per load. So if you've been using more than that, most likely it's a detergent buildup. And even if you're not seeing it on your clothes, here's an easy way to check. Without adding any detergent or any clothes, start a cycle on your washing machine with the hottest water available. Once it fills, let it agitate for a few minutes and then pause the cycle so you can open the door or the lid. If you open it and look inside and see bubbles, that's how you know you have a detergent buildup. At that point, I would recommend running a washing machine cleaner through your machine, like Affresh. And keep in mind, if the buildup is pretty bad, you might have to run a cleaner through it a few times in a row.
If you didn't get any bubbles, but you're still seeing some flecks on your clothes, that's the point at which I would recommend calling for service. Either way, you should be running washing machine cleaner through your machine at least once a month.