Using tap, not adjusting PH

I adjust my Ph religiously. Soil/Soiless is always at 6.5-6.7 and DWC is 5.7-5.9. I have a buddy who doesn't touch his Ph at ALL and he gets QP's off his plants. I talked to another patient who grows in a 50/50 compost mix with a wick system, who also doesn't adjust his Ph, gets QP or more per plant, and produces quality meds.
This doesn't seem right?

There is a lot more that goes into a successful plant than just water.... better safe than sorry on the PH, especially if you are using nutrients.

When your plants are done, check their root development to make sure you are not having issues there.

Are you training your plants with LST or some form of tying down? Is your friend using this technique? This can improve yield also.

Are your plants starting flowering at about the same size as your friend?

What nutes are you using?

Are you using a different light than your friend, and is your bulb still giving max lumens? Do you use CO2, or have intake air and outgoing air?

If you find your friend is getting more yield, I bet you will find he is differing from you in more than just the PH issue.