I had this whole thing typed out and it didn't post.
Basically, I think it's something called Ich. My fish have white spots on it.
My Tiger Barb went missing for a few weeks it was dead and stuck hiding, and allowed the body to deteriorate in the water. I believe that is what started for all my fish to die. Since I found the body 4 fish died and I performed a 75% water change.
My tank has been up for 8 months. Levels are normal, PH is a little high due to the water in my area. But I've been using 50% filtered store bought water to lower ph.
I have 2 Angel Fish (they stick at the top corner of my tank and don't move much)
4 Cherry Barbs (2 died so now I'm at 2) (white spots all over them)
6 Tiger Barbs (2 died, so now I'm at 4)
3 Turquoise Rainbow (1 died, so now I'm at 2)(white spots all over it)
1 Red Tail Shark (white spots all over it)
6 Panda Corydora
1 Blue Powder Gourami
1 Honey Gourami
4 Danios
1 Pictus Catfish (died)
http

/www.my-tropical-fish.com/images/ich.gif
http

/www.google.ca/imgres?imgurl=http

/www.vet.cornell.edu/microbiology/FishDisease/aquaticprog/highlights/Ich/ICH1.JPG&imgrefurl=http

/www.vet.cornell.edu/public/fishdisease/aquaticprog/highlights/Ich/Ich.htm&usg=__a64LoyBTtXm5c-1RDut-5VMte0I=&h=288&w=360&sz=134&hl=en&start=6&zoom=1&tbnid=GlIjCaF_gKEZhM:&tbnh=97&tbnw=121&ei=oxu4ToHwHerm0QGjhunRBw&prev=/search%3Fq%3Dich%26hl%3Den%26gbv%3D2%26tbm%3Disch&itbs=1
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/tropical-fish-pictures.blogspot.com/2010/12/white-spot-tropical-fish-disease.html