how many fish do you have?
how often do you change your water?
some plants are root feeders. your swords would appriciate having some nutrients from under your substrate.
your plants need to have nitrate, phosphate and potassium (N-P-K) they also need micro (aka trace) nutrients. and they need to be available where the plants feed from.
you dont need to stop doing water changes. you can just add nitrate to your tank.