okay will take this info on board i definitely don’t neglect the tank but was told to not do so many water changes and that i should need to do a water change unless something goes wrong, but i clean the tank regularly siphoning the sand cleaning the algae but i run the water through a filter sock when cleaning into a bucket then put the water back in but without all the stuff i just cleaned out. I top the tank up with saltwater not straight salt and i don’t mix it myself i buy the water from the storeThat anemone looks like it is a BTA in very poor shape. In anemone world, BTA is practically almost indestructible in term of ease of care in comparison to other host anemone species. It does not appear to have adequate light or circulation there, but likely that is not make it sick. Anemone just moves if they don't like the current and light. I almost 100% sure that that the problem is in the chemistry.
The OP mention that the tank has been running for 2.5 years. There was no water change in the last 2.5 months. Poor maintained tank has "old tank syndrome" which mean basically "bad water due to accumulation of micro-toxin, and depletion of micronutrients. Turn this around isn't always easy because a lot of the micro-toxin bind into the rock, only release when pH gets low like during the night. Because of this reason, large water changes do not always fix things. This, "old tank syndrome", is a lot more common in tank with sand bed that have been neglected.
LFS alway just test for ammonia, Nitrate, Nitrite, salinity, perhaps phosphate. Testing at the LFS is hardly extensive. It will not pick up cause for "old tank syndrome".
OP mention "...upping my salt and more RO water..." I just hope this does not mean adding salt crystal to the tank.
Concentrate on get the water condition better, however you can do it, or else get him to a new well-run tank and you may be able to save him. When I am talking about getting water condition better, I do not mean just salinity, nitrates, phosphate, but more than the macro nutrient and waste, I mainly concern with the normally unmeasurable trace nutrients and toxins. You MAY be able to correct this with large volume water change, 50-75% changes repeatedly, or else 100% change but you must match salinity and temperature.
Goodluck