Why is my fish tank water cloudy (white/gray)?

I have a 27 gallon tank with a fluval 305 filter running. Many live plants, 6 platies, 3 ghost cats and an aquatic frog. The tank has been running for 3 weeks and I cycled it using the bacterial packets available. For the past few days, it has been a cloudy gray/white, each day getting more cloudy. All water quality parameters are good and I have been doing 10% water changes every few days to about once a week. It began to clear up but then got cloudy again. Why is it becoming cloudy now or again and how long can I expect it to last? If it doesn't clear up, will a water clarifier help or hinder the process in the long run?