Yellowing In Leaves

Remember to get a little bit of the 7.0 Calibration solution. I got both the 7.0 and the 4.0 calibration solutions. Do your best to keep it from getting contaminated. Like just sticking the pen into the main container for the solution.

So don't dip it into the solution ?

Not into the main bottle of the solution. Take a small amount out of the main bottle and put in something like a shot glass. You do not need much.