maintain alk and calcium with a balanced additive,such as two part or kalk and for soft corals i like seachem reefplus amino acid supplement.i am not sure why i get good results with it but i know it makes my soft corals extend polyps farther and color up better than when i use nothing.also softies like some food substance regularly to keep growing at a good rate.but truthfully it all comes down to water quality and i know of nothing that helps a tank that is not doing great as frequent water changes with rodi water and a quality salt mix.also if you give us your parameters it will help people know how to help.hope this helps.