Bangaii cardinal's fin disintergrating?

[fishkeeperpro]

Since thursday of this week, the top fin on my bangaii cardinal keeps getting shorter, ive noticed that the clear bit of fin around the fin in all ragged and the end of the tail is also.

The bangaii isnt showing any abnormal signs, all ive noticed is that a white dot has appeared on his tail about 2mm big, (not whitespot). He/she is swimming around normally (well just floating and swimming when it wants to) and is eating fine.

 

Here are some pics showing you the tail size difference, the top and bottom fin were the same size last week and the top fin was once longer than the bottom fin by a little:

 

 

 

Now the white dot, on 1st pic its been circled and 2nd pic is it normally:

 

 

 

Any suggestions on wha tis may be? My tank readings are fine, i do have an eunice worm in the tank that i ahvent been able to catch, as the bangaii ust "hovers", would it be possible the worm caught the tail fin in the night?

 

Ph-8.2

Ammonia less than 0.01 (my test doesnt have a "0" option)

nitrite - 0

Nitrate - between 1-5

 

Please help

 

Thanks

 

Will

 

 

sorry about poor quality of picas, my parents camera is rubbish (only a 2mp digi )

[fishkeeperpro]

ive just noticed a reddeining in the fork of the two fins on the pther side to the images shown