Hi Mr September!
Looks like the tanks had a time of it but good to see your back on track! The Cal and ALK seem ok, the alk is a little low but the pH seems to be holding and without any hard corals to use it in calcification the only thing binding it would be the coralline algae. This would be so slight that will be fine. As long as the water changes are taking place these with replenish anything that’s used. I would like to know what slat you're using because some are fore use with tap water and have decreased levels of Calcium, Carbonate and Bicarbonate because of the levels in the tap water making it up. If this salt is used with RO water than the levels will be low.
Also you hitchhiking star is an Asterina sea star, while in small numbers are harmless they can and will grow out of control if the coralline algae is abundant because it's there main food source.