I've used the Seachem root tabs with good results... Only issue I've had with them is over time they can discolor lighter colored sand in their direct vicinity--really not a big deal as it tends to not show on top of the substrate anyway and they work.
I might have added too many nutrients. Between adding the tabs and adding "plant gro" about a week and a half ago (thought the excess nutrients were out of the water by now) I think it was too much.