if you have crushed dolomite lime or oyster shells in your soil it will act as a buffer and keep your PH reasonable, a lot of soil already has one of these added. If your water is a 7 then that is perfect for you - adding a slight amount of nutrients or supplement or pretty much anything to your water will bring it down to around 6.5 if you water by the gallon - for your plain watering you could use a drop of superthrive, a drop of mollasses, myco incollent, earth worm casting tea, sillica, sea weed, kelp, or anything else that will not cause burn to bring your PH down to where you want it every time, in my opinion its better then using PH down. Keep in mind totally unnecessary if your dolomite lime is active and working correctly you could just continue to water with the 7 or water with 7 for only your plain waterings.
Either way your results will be good and it would be highly unlikely for you to experience PH problems given your scenario, contrary to popular belief on these forums, a problem with PH in soil growing is a rare oddity assuming your soil contains a buffer and that the buffer is actively doing its job. In hydroponics PH is a common problem and I think it is the hydroponic growers train of thought that seems to perpituate on this forum into the minds of soil growers that somehow PH is a common problem for soil growers when in fact that is far from the truth.