Water tests would help: GH/KH primarily. There are many elements like Iron, for instance, that cannot be taken up by the plant if your GH is too low or high.
You are dosing flourish which is primarily micros, you need to add macros as well for more balanced fertilization of the plants: NPK and possibly iron as well. Flourish just contains micro's, for more balanced fertilization need to dose macro's as well NPK.
Stem plants like swords can get by with just heavy root feeding, but anubias needs water column dosing to stay healthy.
High nitrates can also contribute to algae as well as filters that are not routinely cleaned.