Neglected 125 gallon

[Tbrew]

So, I have been through alot lately and haven't taken care of my 125 reef. I have flatworms and some red algae type stuff all over. So today I'm going to be treating the water with Flatworm exit and carbon. I have not done a water change in at least 6 months. I have prepared 20% new water. My salinity in the tank has dropped to 1.021. The corals are thriving beyond my belief and my 2 tangs, 2 clowns look very healthy. I would like to bring the salinity up, so I made the 20% new water 1.027. Is this a bad idea?

[HPD Turbo]

You should not raise the SG more than .02 at per day or you will kill your bacteria.
Hope this helps.

PD: I would change 50% of water.