PH pen dilemma

I have a PH pen dilemma. Pen 1: Brand new Aphera PH 20 calibrated and reading 7 and 4 in solution. Pen2: Adwa AD12 calibrated and reading 7 and 4 in solution.

As soon as I put them in nutrient solution Aphera reads 6.1 and Adwa reads 5.8. Different nutrient solution Apera 5.6 Adwa 5.4. Tap water (normally 7.2) Aphera 7.1, Adwa 6.1, Looking at this the Adwa is reading low BUT back in PH solution and they are both spot on 7 and 4.

Scratching my head now.

That’s frustrating eh. Any one around you that you could borrow a ph pen? Local hydro shop might have one they will let you compare too.

i have always wondered how accurate these Meters are. I have blue labs.I check calibration once a month maybe. I am in hempys and find my plants suffer at 5.8ph that everyone recommends. But at 6.0ph they are great. I have always wondered if it’s my meter