OK so I'll add another question
I bought a liquid to measure PH.
The guy at the grow store sais to measure only the PH of the water that I'm gonna give to the plants and just make sure that has the proper PH. I'm like HUH? am I not supposed to check the PH of the soil somehow?
I dont feel like investing in more advanced PH meters, they cost around 60$ where I live.
He said I can water the plant and then check the PH of the water that drain from it, is that correct?