a couple on notes/q's...are you rinsing all the dust out of your hydroton before you use it?

go on ebay and splurge on some ph down at least. 8 bucks.
when you but a pen...the good ones come with calibration fluid. I use Milwaukee...strongly recommended over hanna.

blue lab truncheon is the best under 200 dollars.

ph of lemon juice 2.5 ph of baking soda 9.5 - just a note.