Anemone Smaller and keeps retracting

[Gumbies R Us]

I think I found the culprit the Nitrates are at 5.0 does this mean a filter change?

My nitrates hover closer to the zero mark in my tank and my anemone is doing just fine. How old is your tank? Usually you don't want an anemone in a tank under 6 months, they need to be in more established tanks