Loosing its Zooxanthellae.
( The red or green coloring)
( Taken from Joyce Wilkersons Clownfish book)
" Three-Way Symbiosis"
A less apparent but far more important symbiotic relationship exists
between an Anemone and its Zooxanthellae then between Anemone and Clownfish.
Zooxanthellae are Photosynthetic Algae living inside the Anemones cells.
The Algae Photosynthesize and produce glycerol ( a carbohydrate) and organic acids, which the anemone shares in consuming.
This source of nutrition may account for much of and Anemone's nourishment.
The waving tentacles of an
Anemone
may not be there to welcome Clownfishes or snare prey as much as to
maximize an Anemone's sun-collecting surface area and to facilitate Zooxanthellae nutrition production.
The anemone produces ammonia wastes and amino acids which in turn nourish there Zooxanthellae.
A Clown fish may also play a role in the nourishment of Zooxanthellae,
producing nitrogenous wastes that anemones may take up and share with
their Zooxanthellae, forming a three-way symbiosis.

Please read the new section under Zooxanthellae/Article. It is fantastic and easy
to understand.
Click below to go to that section
http://www.karensroseanemones.com/articlezooxanthellae.htm
Below are some pictures I took of some of my Anemones the day they arrived from out of state.
All of these Anemone's survived and regained there Zooxanthellae after good feeding and lighting.
As you can see , they will still retain there Bubbletips even though they are sick.
Keep your water quality high and give them the proper light and food and they will recover.