I'm not going to say your anemone is going to die, due to being in a 6 week old tank, since I generally do not wait 6 months before putting anemones in, but it does sound as though you should have waited. Forgive me if I am wrong but it does appear as though you are new to the hobby, which I assume is the case since you do not know what "bleached" is, you put your M. doreensis on the rockwork (when it is found on the sandbed in nature), and you are mixing an anemone and ray together (Rays IMO are best kept in species tanks or mixed in with bamboo sharks in large aquariums). I agree when others have said slow down, and do some research before making anymore livestock purchases.
Also IMO your lighting is really insufficient for your sized tank, for any anemone species, especially considering long tentacled anemones belong on the sandbed, meaning the light would probably not penetrate to the bottom.
Bleached means that your anemones has lost all of the symbiotic algae which resides in their tissue, which give them their color. This algae is called zooanthallae, and the anemones feeds off the byproducts produced from the zooanthallae. I do not see your anemone making a recovery under the current lighting setup you have.