APEX showing sudden PH drop

[jmags080307]

My APEX has been up and running for about 3 weeks. I received a text alert that my PH dropped from 8.26 @ 3:10 to 7.11 at 3:20. Is that even possible to have that kind of drop in 10 minutes? Unfortunately I don't have another test to compare it to.
Jay

 

[Shanna]

We have had some issues with our Apex probes. It's probably not your water. Check that nothing's crawling on it and that it's properly submersed.

 

[greybolt03]

I have a few sudden drops but nothing that low

 

[jmags080307]

Mine stayed at 7.11 until I recalibrated it. When it wasn't moving I knew it want my tank. Seems to be fine now.

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[Mrx7899x]

Mine seems to says calibrated for a couple weeks then starts to drift, but my probe it pretty old I think its time to replace it.