Feels like Tank is crashing.

Guys and Gals, my tank is just being weird lately
1. My Yellow Tang died about a week and a half ago. I had it about 3 days.
2. My tribal Blenny died yesterday. (This was my first fish and ive had it since june) No idea what happen to it?
3. And now My orchid Dottyback has severe ich.

Is this normal???????? Not sure what to do or think at this point. Everything was PERFECT!

Water is good..there is a very slight sign of nitrate..but nothing super major..i'm working on changing water etc. etc..

Sounds like disease. Ich can kill and velvet is even worse. Gotta QT those fish before adding them to your tank.

If you have any fish still alive I would set up a quarantine tank ASAP and remove all the fish from your display and get them into QT with copper medications. Let your tank be fishless for 6-8 weeks so the parasites will die off. Once you've reached that mark and treated all the fish you can start adding them back to your display. One fish not properly QT'd can reinfect the whole system.

If you're not familiar with quarantine tanks here is a thread to get you started,

http://www.reef2reef.com/forums/saltwater-beginner-articles/95569-procedures-setting-up-proper-quarantine-your-fish-cheetofingers.html