Do i wait to recheck ph level

[timdog4]

Hello, I tested the ph of my water and it was around the 5.0 to 5.5 color range. So I added a couple drops of ph up and retested and it didnt change. I added some more and still didnt see a change. Do I have to wait 24 hours or something, I shook it up but do I need to let it adjust? I am using soil and was testing before feeding. It is distilled water with grow big and couple drops of superthrive, so I was surprised to see ph level so low.