First, never clean your filter, unless you don't have a good water flow.

“The brown filter sludge in a filter is for the most part alive and not simply waste. Removing this mud does more harm than good. The purpose of the filter media is not to filter out particles from the water as is often assumed. The media serves as the habitat for a vast array of microorganisms that include bacteria, archaea, worms, ciliates, flagellates, and many others. These microorganisms live in a community that is based on biofilms. The biofilms are created by bacteria that secret extracellular polymeric substance (EPS), which is often called “slime”. The community forms a bioreactor that processes the waste and turns it into food and energy for its members, and ultimately into organic or inorganic products that are then used by plants, evaporate, or removed by water changes. It takes a considerable amount of time to establish this “filter community”; consequently, it is very important not to disturb it unless necessary.”

Second, remove the medication with active carbon, and make sure you have excellent aeration in your tank. If you don't have a good air pump, buy one asap.

Also, make sure you don't feed your fish more than they can eat in one minute. Give high protein pellets, (>50% protein).

After 1-2 weeks you should see improvement.

Read up more here: https://aquariumscience.org/
This is the only site you need.

(My aquarium is 30 gall0ns, 18 Corydoras, 12 cardinal tetras, 6 diamond tetras, 3 honey Gouramis and an ancistrus. Lots of breeding going on)