Whenever I check my runoff pH it's usually lower like that. I think it's due to all the excess salts it's washing off that lowers it. I consider runoff pH arbitrary and don't focus on it much unless I have no other options. You could grab a soil pH tester if you're worried about your soil pH. I use a kelway one and it works great.
Oh and as far as your over watering I used to have the same issue constantly till I upgraded to rain science grow bags. Makes it much more difficult to overwater I highly recommend them over fabric pots.