fish dying (long Post)

[MitchM]

PH is too low.
Ammonia should be zero ( how long are dying animals staying in your tank?) Look for that yellow tail damsel. That ammonia number says it's in there somewhere decaying. Get him out of there asap.
SG is low (should be closer to 1.026)
Change out more than 5g at at time. You should be changing 10 - 20% each month. You have a high bio load and you're feeding quite a lot.
Make sure you have a lot of surface water movement. How slow is your turnover?
What are your calcium, magnesium and alk numbers like?
Which salt are you using?
What is your regular maintenance schedule?
Do you have any sand and are you cleaning it regularly?
Are you running any carbon?

(not that it matters, but Calgary still has fluoride, it will take probably a year before they stop adding it)