Skin disease and fin hole. Please help

[briankchung]

My L 24 female have this skin cloudiness, discolouration and hole on the fin. One week later the mate start to have the same problem. The fin did not full rot but started with a hole the a section of the fin disappear. I raised the temperature to 30 degree cel and using waterlife Myxazin for the 4th day.
Anyone have the same problem and how to cure?
Thanks for help guys!

[briankchung]

Here are more information on the tank

1. Water parameters
a) Temperature range. 28-30 cel
b) pH. 7.8
d) KH 3
e)Ammonia 0, Nitrate p, Nitrite 0
f) Water change frequency 50% per week

2. Tank set up
a) Size. 118cmx67cmx77cm
c) Filtration 900L per hour sump
d) Furnishings. 2 caves and drift wood
e) Other tank mates. No
f) How long has it been set-up? 2 years
g) When was the last new fish added? Never
h) Foods used and frequency? Daily or every other day

Thanks for help

[briankchung]

Sorry correction 6000L per hour