I agree with theUK 5.5-6.5 is fine. If you're a perfectionist like me 5.8-6.0 is optimal. Run a little more water through than usual and that will raise it. 2 options that work well. Run double your usual watering through. So 1/2 plain ph water at about 6PH then your feed at your desired PH 5.8-5.9. Other option is to flush. Run 3x times pot volume at desired PH then feed.
I'd probably go with the first as you dont have any issues yet. You may have a salt buildup causing the PH to drop. Personally I'd do something about it to prevent issues down the line.
Dont worry about overwatering, you have drainage and if you follow your usual watering schedule it will be fine. Overwatering happens based on the frequency of watering, not on the volume watered. Just be vigilant with the feed after as it way take a little longer to dry.
Hope this helps 🙂