So many questions... fish

Hi everyone. I do hope I am writing this in the right place. I am only a newbie of salt for 2 months and a newbie to this forum for 2 minutes. If I need to move this, please let me know. Any who.. we have decided to finally dive into the world of salt after many years of tossing and turning. We got started with a 29 gallon bio-cube with all the stock lighting. The shop we got it from tested our water weekly and we added turbo snails and crabs after the first week and the second week a bicolor blenny, 3 coral and a RBA. To try and keep this short, after about another 2 weeks, everything still tested good so we added a standard clown, a hippo tang, bangai cardinal and a mandarin. The bangai died in 2 days. Never saw him eat and he was small. We were told though he was tank raised and eating at the store. The hippo got ick and 3 weeks later still have it, despite the garlic infused seaweed, ick food and even brine that we feed the RBA. She eats like a pig so we are told she will eventually snap out of it but it's common. The bicolor blenny died from the ick. Stopped eating. No hope. Everyone else seemed happy. A week later the mandarin died out of no where. We have copepods in the tank as you can see them on the glass and he was pigging out on brine as well. No signs of ick. Mystery to us. We have been testing our water and even having the store test it all during this process. Everything is testing fine. We were told to get a cleaner shrimp as a tool to help. He died in less then 2 days. The clown is now covered in ick as the hippo still is not cured. I have no idea what is going on or what to do.. everytime I go back to the store I get NEW information. Example: My fish still have ick 3 weeks later yet eating well.. how long does this take? Store: What's your tank temp? Me: Huh? I donno. You never mentioned temp. Store: Oh no.. that's critical. You need to be under 80 for your reef tank. Hours later.. I call. We are at 81-82 in the morning and 83-84 at night. Store: Oh that's to high. Here's your shrimp. Me: Will he be OK? Store: Yup, just acclimate for an hour. DEAD!

So here are the specs:

Water temp: 81-84
Lightings: Blue fan 10 hours, white light 6 hours
Nitrates: 10 or less
Phosphate: 0
Salinity: 1.022

This is all we have been told to monitor and even the temp we just started doing the past 3 days.

I'm getting very frustrated. The ick I understand why somethings happened but shouldn't it be gone by now? The shrimp? The mandarin?

Luckily, the coral is growing great, I can see lots of new growth and the RBA also seems to be doing great. Any advise is welcome as I'm starting to question the store. I trust them.. but feel the important information is being trickle fed to us or I go online and read stuff then question them.

Thanks in advance and I apologize this was so long