In my opinion, in Hydro, any pH between 5.5 and 6.5 is OK, 5.8 to 5.9 is best or works best for me.
Newborn Babies are born hungry, ready to eat, but they can not handle a T-bone steak or a Mcdonalds Full Meal Deal. You start them slow and gradual.
Mine sprout with two round leaves, do not count those as leaves. I wait until the 2nd or 3rd day, when I see two full leaves, and I add 1/4 strenght nutes. I wait until I see the 3rd and 4th leaf, or a 2nd node about two or 3 days later and add 1/4 again.....adding 1/4 again in 2 or 3 more days until I am at Full Strenght.