What Harddon said.

Don't use distilled water. Your plant likes the micro nutrients in regular water anyway.

3 is WAY too low for your ph. I would use regular tap water. Mix it up and let it sit out over night and see if the ph creeps back up. The ph buffers in the tap water might stabilize your mixture over time.

If the ph is still too low the next day, then use ph up to raise it. But make sure it's within scope before you use it on your plants.

To test your meter, try testing some normal tap water. Normal tap water should be neutral...about 7.

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I was at the pet store buying a hamster and all I could think about was what kind of nutes I should get and how long I should keep it in veg for. I knew I had to get the hell out of there when I started thinking how I was going to LST the damed thing.