Since you're using a hydrometer make sure there are no bubbles in the body of it or on the arm, make sure the temp of the water is the temp of the tank(so it'll be accurate) and don't do a huge water change.I will do a big water change today. I have a instant ocean hydrometer . A cheap one. I never pour fish water from a different place into my tank. This is my first saltwater aquarium. I did it to save a fish .
What are you making your water with?
If you want to upgrade a little bit and not put too much into it(I'm assuming you want not so much coral but more fish) get a refracto and it should help. However, with the anemone its possible that many different things could be causing it to be unhappy and without the more precise equipment its harder to diagnose.