White Cloudiness - Bacteria or Minerals?

I've googled this subject and found some things about bacteria being a
possible cause. Here's my situation:

- Did a 25% water change with relatively high pH tap water (over 7.4).
Water was clear before the change, but has gotten more cloudy over the
several days since. It is not extremely cloudy (can easily see through the
tank).
-Tank pH before change was maybe 7.1. pH after was 7.3 at most... not much
change considering the tap is well over 7.4, althought that is the top of my
pH scale.
- Tank is cycled, ammonia at 0.
- 55 g tank still with pretty low fish load, fish seem normal.
- I do not have a hardness tester but the tap is quite hard and the heater
has a white crusty precipitate on it often that comes off with little
effort. It is rock-like, not a soft precipitate. I dropped a sample in
some vinegar to see if it would fizz, but it didn't. So it is either not
carbonate based or the "apple" vinegar I used was somehow stale (I think it
came with the house 25 years ago).

I know that it might be necessary to provide hardness of the tank water and
tap but l haven't gotten a hardness tester yet. I do not overfeed these
fish (flakes), but occasionally feed extra bloodworms. I know one person
seemed to think the water with her bloodworms might be causing a problem,
but that sounds like a stretch to me.

Any thoughts?

thanks,
dwhite