[Eco complete, liquid ferts etc..]

I have a Fluval Vista 16 gallon tank with 8,000k led lights. I use Caribisea complete as my substrate 2" deep at least. I use root tabs since the substrate is almost a year old.  Plants include Water sprite, water wisteria, crypt wenditii, and crypt spiralis. Got a case of black beard algae and now hair algae (my marimo moss ball turned black).   I'm doing a 20% change once a week.  Nitrates a little high.  Ammonia zero.  Lights are on 6 hours a day.   What else can I do to get the balance.  Was thinking of skipping root tabs and just using liquid ferts once a week (most of these plants are water column drinkers no?) Thanks so much!