They're looking really good.....yes, sounds like you need to replace your probe. You can buy some very inexpensive ph testers at your pet store for aquariums (NO fish ph adjusters....only testers for fish ok) and keep them as a quick back up and calibration set.

Oh yeah, there's ALWAYS something else to buy. :thumbsup: Have fun.

PS...keep your ppms up to the correct level and the plants will grow faster and be happier. (when you add water add your nutes and adjust ph to it first)