Is PH the only test that is affected by high CL

Yes ok at that FC level.

At FC of 13 if you read the color quickly on the pH test you can get a good reading. If it looks purple and very high then beware.
 
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The TA test can be affected at higher TA levels, making the indicator colours look differently. But this can be easily fixed with an extra one or two drops of R-0007.

But shouldn't be a problem at FC 13. And you'd notice the difference.