Highly acidic results despite very alkaline diet

I use PH test strips first thing in the morning as directed, and despite my highly alkaline raw food diet, the results are always as acidic as possible. I eat almost all vegetables, seeds, sprouts and some fruit. I drink lots of water.
I've taken readings later in the day, and the results are usually somewhat alkaline then, but according to the strip directions, the truest reading is first thing in the morning.
I'm concerned about this. Does anyone else have any experience or input.

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