Tetra pH Minus okay for plants?

Repotted, less water, no nutes and still the girl is suffering. My tap water is around ph7, is use Tetra (for fishtanks) pH Minus to bring the ph down to a more respectable 5-5.5. I than get a runoff of around 6. Question is, is this stuff usable for plants? I’ve looked in the larger garden shops (in Belgium) for something more suited for plants before I order online, but nada. Something is still not right with my girl.

it works fine fish are very sensitive and as for your ph unless you are growing in Coco or hydro 6.2-6.8 is the range you want your ph at

Thanks! I tried Coco and it was a disaster, so now I’m back to good ol’ dirt. PH seems ok than.