PH run off problems! Experience needed

[buddha buds]

Hi, i am an averagly experienced grower, in most senses i know and am confident in what im doing, but ive come across something that is slighlty holding me back.

When i water/ feed my plants ( in soil) i allways adjust my water to 6.5 (and adjust after nutes), but the other day i checked my runoff for first time on 4th crop and ii notcied it was at 5.1 even though everything i have put into the soil has been 6.5

Why is this ???? Is it a problem???? how to fix if so ???

Many Thanks.

 

[Folanabing]

What soil do you use? Have you given any nutrients already?

 

[buddha buds]

Hi i use biobizz light mix soil , biobizz nutrients, am nearly 4 weeks into flower.