I’m not an expert on the differences but what i saw is, the calibration feature is real nice on GS4 1 button push and it auto calibrates no second button pushing, EC is displayed as all charts show in .1 increments PC 60 you needed to move decimal and use ppt. Also a single point calibration for EC. It describes the GS4 as specially for testing mixed solutions for hydroponics growing. It is much easier to read and makes for less errors when reading numbers. As for your PH issues i use coco/perlite only. I have heard from some of the experts on here that they advice against mixing soil and coco because it can cause ph issues. The problem is coco and soil have different ph requirements and water requirements and coco requires calmag in every feeding etc. I’m not sure if your hand mixing or using promix but I’m not a soil or promix guy. I will tag a couple experts that should be able to shed some light on your issues @Growdoc @OGIncognito
Hope the information helps grow bro
