Everyone grows differently, and different techniques work well with different nutrients, with the nutrients i use, What I do, set it at 5.5 when using tap water, the ph will gradually fluctuate between 5.5-6.0 over a week period, usually flucuates up, then I top off with 5.5 ph water.

Having a slightly fluctuating ph allows for better nutrient absorption over a larger range.(In my opinion.)
One thing to consider though, small amounts of water will have larger fluctuations, than larger amounts, which can cause problems if the swings are to extreme.