Down to 4.7 on the low end is fine with 5.2 being ideal and I wouldn't go much higher than that. When unbuffered, pH can have wild swings in acid/base concentration at neutral pH of 7 due to just the water's natural concentration of hydronium/hydroxide and pH being on a logarithmic scale. A pH buffer changes all that. Drop in some lemon juice or citric acid to get it where you want it and call it good. The yeast is fine being off a few tenths.
