It could be green water due to the increased light. Take some water and put it into a white container to see if it is green water.
Ditto. It only takes a week or two. Like Turbosaurus said, it won't come back once your tank settles in. It shouldn't ever come back if your tank doesn't go through any big changes (bacteria die-off in the filter, lots more fish added, large plant dying and not being removed, etc.).You can also just wait it out and it will do its course and then go away