Soil PH needs to be increased. What do I do?

Just raise ur ph level to 7 for one watering the continue to water at 6.5 that what I would do

Depend on your tap water ph, but simply tap water ?

Yeah, I'd use water that's pH'ed to something like 6.7 or 6.8 or so. After a few waterings you'll find the soil pH will stabilize upward.

Dolomite lime will help stabilize your soil ph

Io personalmente non mi preoccuperei troppo il pH ideale da che so e tra il 5.5e il 6.5 dunque sei nel range Riguardo le piantine non sempre hanno la stessa risposta e possono variare anche se dello stesso ceppo (a volte sembra che abbiano un carattere tutto loro) 🤠 buona fortuna e raccolto abbondante 👍

Watering with a higher pH, start watering at a pH of 7 and you should see the pH rise

Easiest way is to water with alkaline water,probably your tap water.salt build up seems to be the reason ph dropped to that point.always get some runoff in those small size pots because this happens quicker than bigger ones like 3-5 gal