A tank is not considered 'established' until it hits the 6 month mark.
A lot happens in the first few months as a new micro bio-climate is established.
A Byron mentions, it is a common misconception that cloudy water is relative to the N2 cycle. It is not. Cloudy water is the result of a bacteria bloom of facultative (decomposition) bacteria. These are the critters that break down and decompose waste (organic compounds) products. Some are confused thinking that there new tank does not have organics in the water....but it's often in there in all but the most finely filtered waters.
Although cloudy water might be blamed on adding fish, the most frequent cause is over feeding. Even if/when all food is consumed, fish will over eat and produce more waste. If all food is not consumed, or the substrate allows uneaten food to quickly sink out of reach, excess decaying organic material may cause a bacterial bloom of facultative bacteria.
Although unsightly and not desirable in a display tank, cloudy water is rarely harmful to fish. However, it can underscore a situation that may become a bigger problem. Excess decaying organic matter produces [more] ammonia, nitrites and eventually nitrates which can all become harmful. Obviously in a tank that hasn't cycled this can be very dangerous.
Usually cloudy water resolves in a few days assuming good tank housekeeping is in play.