Sourdough Starter Mix Sourdough Starter?

Sourdough starter? - sourdough starter mix

I have an entry in the yeast for the first time a few days ago. The first night was booming and bubbling, the next day, which had been created, which was small bubbles. In the Old Testament seems second night they had separated. After mixing (mixture i tid), the starter again looked good. My question is this normal? Thanks