Like others said, it's bleached. As for the cause, I'm not exactly sure however I do have my theories though. (I can see this already turning into a debate with Todd saying it's not the lighting while others saying it is the lighting.) 
Lets break it down:
When the OP got the RBTA, it's more then apparent that it was a healthy RBTA full with zooxanthellae algae. Not only do the latter pictures portray a very bleached RBTA, they also show a diminishing size of the RBTA. That's starvation. Based off the picture, the RBTA is at the very bottom of a 30 inch deep tank. Whether or not some of you think this is the cause, I honestly think the lighting could have something to do with it. I think there is another underlying factor but I'm not sure what. Not enough details have been given out yet. Parameters with numbers of the tank are useful but are not everything. Something is obviously stressing out the RBTA, whether it may be light, something else or a combination. I say it's a combination of problems.
Edit: I just read that you've had the anemone for 6 months. Any serious problem would have killed an anemone much quicker. Six months is usually about the time frame it takes to show drastic signs of starvation. Lets see what others say. Try moving the rock that the RBTA is attached to towards the upper half of the tank. If the rock the RBTA is on is essential to the integrity of the rock structure, then trying moving the RBTA by itself instead.
Lets break it down:
When the OP got the RBTA, it's more then apparent that it was a healthy RBTA full with zooxanthellae algae. Not only do the latter pictures portray a very bleached RBTA, they also show a diminishing size of the RBTA. That's starvation. Based off the picture, the RBTA is at the very bottom of a 30 inch deep tank. Whether or not some of you think this is the cause, I honestly think the lighting could have something to do with it. I think there is another underlying factor but I'm not sure what. Not enough details have been given out yet. Parameters with numbers of the tank are useful but are not everything. Something is obviously stressing out the RBTA, whether it may be light, something else or a combination. I say it's a combination of problems.
Edit: I just read that you've had the anemone for 6 months. Any serious problem would have killed an anemone much quicker. Six months is usually about the time frame it takes to show drastic signs of starvation. Lets see what others say. Try moving the rock that the RBTA is attached to towards the upper half of the tank. If the rock the RBTA is on is essential to the integrity of the rock structure, then trying moving the RBTA by itself instead.
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