IPhone 4 Vibration Very Weak?

I got my iPhone 4 in November and lately have been noticing that my phones vibration is very weak. I just got my phone in November. Is this covered under warranty and if not how much would they charge me to get a new iPhone. Also, if I have the black iPhone can I change and get the white?

The vibration is pretty weak on All iphones and they also have low sound quality

  • Why is the iPhone battery so weak? You have to charge it up all the time so why haven't they got a battery that can last at least a few days?
  • Why is the battery on my Iphone 5 weak and half of the screen has a blue tint? The battery doesn't even last a 1 day! And i'm not actively using it either. After holding the cell between my shoulder and ear for half an hour the right part of screen has a dark blue tint and it doesn't go away. WTF
  • Why do I do this? I'm very very very tired yet I don't want to sleep? I want to sleep because I'm practically blinking and bobbing my head side to side like a drunken man but I just don't want to sleep. I watch tv or go on Facebook or play on my iPhone. And I'm starting to get dark circles. And as a guy I don't wear. Concealer or whatever
  • My iPhone suddenly has weak Wi-Fi signal strength? This has been going on for about a week now and it happened suddenly. My 3GS suddenly has terrible Wi-Fi signal strength, meaning that if I'm in my room now, I can't get Wi-Fi while sitting on my bed. I have to be on the same floor basically as my router. Is there something I can do? Is there dust blocking something? Tips please?