I hadn't seen anything about cloudy water before now (but I'm a notorious skimmer, so I might have missed it).
How long has the water been cloudy? Cloudy water could be several things, but a bacterial bloom is the first thing that comes to mind, caused by too much organics and not enough surface area for the bacteria that consumes the organics to grow on.
So, back to the basics - what type of filtration do you have in this 28 gallon tank? How much live rock? What substrate? Also, I would imagine that your MH lighting has increased your evaporation rate. What are you using for make-up water, and what are your current water test readings (ammonia, nitrite, nitrate, pH, and Salinity for starters)?
Kevin