How soon to add root tabs?

[cardiocentric]

I bought some flourish root tabs yesterday and I was wondering how soon is too soon to add them? Should I let my plants use up the minerals/nutrients in the substrate first and then add them, or go ahead and give them the extra fert and add them now? Also, is there such a thing as overfertilizing? If I do the liquid AND the tabs, is that going to be too much? My sword plants are looking a bit on the down side, but it might be the shock of being planted in this tank. I was hoping the tabs would get them perky again.