4 Wpg is a lot, riccia and glosso can grow in half of that with plenty of c02 . If you have a drop checker then add as much c02 as you can to get the DC fluid turn green and add a bubble of c02 each day , making sure the fish arntgasping for air. Every tank is different so nobody will have a lot of answers ... It's a trial and error situation and one of the few things that your on your own with in this hobby. Regarding dosing , just follow the seachem chart for a week or 2 and see how the plants react, if you need to add more of one fert then do so. Again every tank is different.
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