Xmas Moss Starting To Get Brown Dying?

[Deleted member 107737]

Hi All.
 
I have a 150litre 40g tank with good lighting and i add fert as well.
 
could anyone suggest why my xmas moss looks like its dying??
 
Looks simular colour to below - browning
 
http/www.google.co.uk/search?q=dying+xmas+moss&hl=en&source=lnms&tbm=isch&sa=X&ei=Kb9iUdrECI7ZPZGqgIAI&ved=0CAcQ_AUoAQ&biw=1920&bih=976#imgrc=vqoYA9hzUDov4M%3A%3B6Vc4Lwvjwb0aJM%3Bhttp%253A%252F%252Fi42.photobucket.com%252Falbums%252Fe321%252Fmessy_da_legend%252Fmoss3.jpg%3Bhttp%253A%252F%252Fwww.aquaticplantcentral.com%252Fforumapc%252Fplant-id%252F41470-moss-id-greenline.html%3B600%3B400
 
Ive got java moss and that grows just fine.
 
thanks,.
 
dave