Hmm... several possibilities,,
1. Its a bacterial bloom.... but this doesnt seem too likely given your readings, unless you are overfeeding or not doing regular waste removal (water changes/gravel vacs)
2. Its overly filtered (ie. too much current) this can cause the debris that usually settles into the gravel to stay suspended in the water column... again not too likely because the filters should be removing this
3. Its from the gravel or decor... I see a lot of white gravel, rocks, and decor... the paint used on these could be flaking or dissolving into the water... this would probably be evident if the filter pads look like they are covered in white dust
4. The use of
zeolite crystals in the filter can cause cloudy water... obviously if you dont use zeolite then this doesnt apply
Any of these things, and a few others that are less likely, could all cause white cloudy water... some tanks take what seems like forever to finally clear up, while others never even get cloudy.
One final thing... are you replacing the carbon filter pads frequently and or all at the same time? If so, then you may be stalling your cycle out and keeping the tank in a neverending mini-cycle.... take a look at this thread about filter maintenance and see if that could be the problem =)
Filter Maintenance