any suggestions on a better one
IDK what your budget is.
For $20 to $25, you can get a Milwaukee pH600. It doesn't have a replaceable probe, but probes generally cost more than this meter does, so that's to be expected. Reads to one decimal point. Fairly accurate. Single-point manual calibration, which means you have to dunk it into a sample of pH 7.0, then use the included screwdriver to adjust a little screw until the display reads 7.0. I don't believe it has ATC (automatic temperature control), but you won't be dealing with temperature extremes, so your reading won't be skewed to any significant degree. I don't remember whether or not this one is waterproof.
For $50 to $65, you can get a Milwaukee pH56. It
does have a replaceable probe (around $30, IIRC). Reads to two decimal places, and is very accurate. Double-point "automatic" calibration (you just basically push a button, then dip it into a sample of pH 7.0 and, for our purposes, pH 4.01). This one does have ATC - along with an accurate readout of your sample's temperature. It's waterproof, so if you drop it into your nutrient solution, no worries. Oh, and it has automatic shutoff, too.