You really need to post a number. The "green area" is often far too low for seastars. So try and get a number, and specific readings on your water quality. It could be that your tank is still cycling, and so there is a major risk to all of your animals.
The acclimation of the star was very short
Specific gravity often varies depending on what type of animals you want to keep. If you want any sort of invertebrates or corals - snails, seastars, etc - then it should be 1.025-1.026. Fish Only systems are commonly kept much lower, 1.019-1.023...but this is too low for invertebrates and can be fatal.
Specific gravity is related to the salinity of the tank, and some meters will have both readings available. So if "30" is specific gravity as in 1.030 then it is too high. If it is salinity, then it is, IMO, too low.