I lived that problem. My 2 observation to solve the problem where 1: overfeeding 2: lack of microfauna.
I cut back on feeding, tried to target feed as much as possible. And promote microfaunus as much as possibilus.
At the moment from all the ones I could have, seed shrimps are doing very well, their population made me realize how much I was overfeeding and at the same time took care to break down every left overs, leaving clean roots, wood, glass and decor. But created a lots of nitrate when exploding. loll. They are a lot more discrete than other pods and worms. And do a lot better job.
For a couple months I been relying on that to gauge my excess of nutrients.
I don't know what fish are in the tank, But. You could also trow a handful of shrimps in there. They will move that mulm into your filter for you.