Use either water. It'll make no difference, as long as you pH first. Candidly, it sounds like you've already resolved the blood meal overdose, but drenching with pH 6.5 will help toward getting your soil pH in line. I wouldn't plan on watering for 2-3 weeks, but you'll have to judge. Your soil will be fully saturated and your tiny plants just don't transpire enough to get rid of the excess, so keep your eye on it, but don't jump the gun and over water again. Your babies need to develop some roots and a drying soil will encourage that.
I've never used any of the commercial nutes so can't help you with your Fox Farm questions.
Don't kick yourself over this. Very common mistake for new growers.
