white cloud with green edges to fins

Question
Hi, I have had 2 white clouds (one is a golden) in a 2 gallon tank for over a year.   I've just noticed that the edges of their fins have a  whitish/bright-greenish color, upon closer examination it appears to have some substance to it, kind of like a tiny piece of cotton has been added.  The golden's bottom fin appears very thin and doesn't have much color.  I've looked on the web for fresh water fish diseases (was afraid it was ich) but am not sure what it is.  They are eating normally, and exhibiting normal behavior. The tank had gotten really dirty (algae starting to show up on sides) so I did a full water change about 3 weeks ago and I've been replacing evaporated water with bottled spring water weekly (about 10%).  We have a small tank heater that is set around 70 degrees.
Would appreciate your best guess and recommended treatment.
Thanks.

Answer
Hi There,

This sounds like fungus. I recommend adding some aquarium salt which is available from your local fish store.
Please do not use bottled water as it lacks essential nutrients for aquarium fish.
Tap water with added de-chlorinator is fine.   
Keep up with the water changes do about 50% every day and then slowly decrease to every 2-3 days until their fungus has disappeared.

Hope this helps,
Chloe :)