Lurking: Back in the Hobby....Need Advice

Hi all, I've been lurking around this news group for a little time. Thanks
for all the good posts, they have helped me tremendously. I have just
returned to the hobby after being out of it for over 15 years. Here's my
dilemma:

I have a 55 gallon tank with an U/G filter with a 160 GPH power head.
Additionally, I have a TetraTec P350 external filter that has been doing a
great job. The tank recently cycled and shortly thereafter the water began
to cloud. In the tank, I currently have:

1 medium Angel
3 medium Platties
2 Pearl Gouramis
1 Female Sword Tail
2 Cory Cats
1 Male Betta
1 small Pleco

Tank stats:
Ammonia = 0
Nitirtes = <.5
PH = 7.6-7.8
GH = 125
Temp = 76F
Last water change was late mid-late January.

I live in Phoenix, so with the warm weather, I am replacing about 1/4 inch
of water every 4 to 5 days. Any ideas what could be causing the cloudiness?
The water seemed crystal clear until the tank cycled........

Thanks all!

AJH