At 3 weeks you shouldn't have anything in the tank, it can cycle from 3-6 weeks and then only a cuc. The nem is very bleached, your tank is a year too new, your lighting is not enough and a long tentacle anemone is not the easiest to keep even with mature experience reefers. If you want to be successful, take EVERYTHING back, and lets start with type of water you are using, current parameters, ect. It takes years to have a success reef, not weeks. All this hobby will do in a hurry is drain your bank account.
The lost of color or “bleaching” is a result of the loss of an anemone’s zooxanthellae. This can happen for a number of reasons such as excessive temperature changes, excessive lighting, insufficient lightning, physical stress, excessive salinity, etc.
Just like corals, anemones use their zooxanthellae to feed on light. The other part of their nutrition comes from meat. Unfortunately, they cannot survive solely on captured prey as their primary source of energy. An anemone without zooxanthellae is usually on the brink of death so:
Bleaching can be reversed, but it takes commitment and time. First thing to do is to is to provide excellent water quality and optimal lighting. If you fear your light is too strong, you can simply reduce the photo period and increase the time slowly over a couple of weeks. This will allow the anemone to addapt. When the light is too strong, the anemone will usually hide from it. The anemone should also be feed in small quantities on a regular basis (3-4 times a week) until it’s color recovers. This will keep it from starving since it dosn’t have it’s symbiotic algae to help out.
They can slowly come back with pristine stable water conditions and high end lighting, they can survive for 6 months bleached but if they don't get their zooxanthellae back they will not survive. Thats why they are not recommended until the tank is stable without parameter swings. Plus probably 80% are bleached as they do not ship well and lfs
owners don't even know that they are bleached, and what to do about it. I have a tank full of nems and I am lucky to test once a month as my tank is stable and even more important, I know the tank, and my equipment I have eliminated parameters swings. But that all takes time, learning and experience. That why we suggest to wait a year, not just for parameters but to get to know your tank and all of its idiosyncratic. Ok, off my nem band wagon
just saving the worlds nems 1 at a time