Fluctuating PH levels

Probably because you are yo-yoing your ph ha ha. It's a yo-yo yo. . I did it when I was first growing hydro. one day I'd be adding ph up the next I'd be adding ph down. constantly chasing the PH.. Less is more.. Let it settle and use water to raise the ph where possible.. Also use like 0.1 ml. Give it a good stir and wait to check it Give it a half hour to stabilize and be patient with it. Rates of transpiration will affect PH but if your plants are small chances are if your ph is going up and down it's from something you are doing. Or possibly a bacteria issue. But usually PH is relatively stable in smaller plants. Ie. I don't do daily check on ph until they get bigger. And on a side note "ph perfect" is bs it's just loaded up with Ph buffers beforehand and is counter productive to given growing environments and conditions.