Extremely low ph this year

Only way pH drops is you add acidic products.
I would suggest removing the Pentair 320 inline chlorinator from your signature, it implies you use trichlor.
 
I assume the test results you showed above are from now. And that the water is clear, no algae.

If so, then the pH might be a bit low due to rainfall. Use some aeration to raise it.
 
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