I am with Chopstick Mike - what are your water parameters? 'all ok' isn't enough information.
Really it is usually a few simple things that create cloudy water.
1. 'New tank syndrome' as in a bacterial bloom that presents itself in the water column giving the water a cloudy appearance. How long has the tank been set up?
2. Inadequate mechanical filtration leading to tiny particles being suspended in the water column. Again, what filtration are you running?
You said the tank has a breeding pair of JD's in it, I am guessing that they are digging around in the substrate quite a bit. Is this the source of the cloudy water, perhaps disturbing the substrate suspending particles that would otherwise be trapped in the substrate?
A side note, I think it is a good thing that stores do water testing for customers. But I think that this is a bit of a double edged sword because people become reliant on this, and fail to learn the basics of fish keeping themselves.