Still early on. I might be tempted to add another shrimp but have you considered adding a small 1 to 2lb piece of good LR (maybe you have already?).
I wouldn't worry about pH at this point. Whether you do WCs during the cycle or not is a debated topic. I usually say do WC's during the cycle to save as much life as you can but since your tank started with just dry rock, I don't think it will matter. Think I would try adding another chopped up shrimp to see if I could cause a spike and also add a small piece of good quality LR.