Sourdough starter stopped growing, is it normal?
Nothing that happens in a starter in the first few days is normal, in the sense that it doesn't behave like a mature starter. During this time, the bacterial flora in the starter is in constant flux, and you need to wait until the desired bacteria have prevailed, which will take some time. 

It is not impossible to do something wrong, but you will only know it when the starter has stabilized, or rather failed to. Until then, just keep the regime exactly as prescribed, no matter what visible changes happen.