Water fresh out of the tap is usually higher than normal Co2.The Co2 drives the pH down. Once the water is released form inside the pipes it will equalize gas levels with the air. As the co2 levels drop the pH rises. There can also be some additinal issues with municiple water sources, some of them phosphate buffers whach can be unstable and allow swings also.
Set you tap water out overnight and see what it tests in the morning. If it equalizes and does not increase then there is something in your tank dissolving and rasing the pH. At the pH reading you have, I would lean more towards the Co2 in tap idea though.
As far as the cycle, Carbonate is consumed by our bacteria and especially in the fishless cycling method if we start with low Kh (corbonate hardness) levels, the process of ammonia to Nitrite to nitrate will deplete the KH which then leads to a pH drop and quite often a stalled cycle.
You do not need to worry about such an occurence at all. The pH levels you are listing normally indicated a high KH level (pH and KH go hand in hand). So the chance of depleting Kh is slim to none in your case. If you see pH drop down to the 7.0 range or below, I'd be quite concerned.
dave