Keep in mind that when vinegar is used as a herbicide, the contentration is fairly high, and you're supposed to use it when the sun is out. Many things that are fine or even good for plants are toxic at high conentrations. I've given a fair amount of vinegar to shaded weeds, and they were fine (they didn't even flinch). I imagine a little calcium acetate on the plant isn't going to hurt it. Fertilizer foliar sprays generally aren't done when the sun is out, and the concentration is very low. So, you're unlikely to kill the plant, unless you use the wrong ratio of fertilizer to water and/or apply it in the sun.

Heinz doesn't make anything called "Pickling Vinegar" and neither do any of the other reputable brands. Allen's Brand isn't quite so clear about what its ingredients are, its distilling process is, or its % of stabilization so is on the 'iffy' to use list. Some sources list its acidity as 5% and some as 7% and some sites list it as having a petroleum-based distilling process (not recommended). Vinegar comes in 2 forms - white or cider (the brown) and are labeled as such. Both are distilled, are interchangeable in recipes, and both are stabilized at 5% acidity (which is the important point). The only difference in white and cider is the taste and the color. But there are some off-brands of vinegar out there and Allen's is one of them with the label "pickling" on them. If they are labeled as 5% acidity, fine. If unlabeled as such or show a lower level of % acidity then you shouldn't use them. If labeled as 7% you can use it but must keep the same measurements called for in the recipe and the taste will be changed substantially. If you reduce it it is a do at your own risk issue because its stabilization method is questionable. Personally I would return it and exchange it for Heinz. Dave

Water supply is not so much the factor for laundry alkalinity or acidity. Neutral pH is 7. Pure water is 7. Atmospheric CO2 dissolved in water (such as rain water) may make it slightly acidic (maybe pH 5.2). City municipal water supply may be treated to maintain between 6.5 and 8.5 pH per EPA recommendations (which is not a requirement). Detergent (high pH, typically 10 to 14) makes water alkaline. Vinegar is an acid (low pH, approx 2.5 for distilled white). The weakened acidity of diluted vinegar in the volume of a washer's rinse water neutralizes any residual detergent alkalinity toward neutral pH. Laundry sours or neutralizers are often used by commercial laundries, particularly when processing linens such as towels and sheets, in the rinse following the detergent wash to counteract the alkalinity of the (stronger than normal household) detergent. Some neutralizer/sour products also contain fabric softener components, or fabric softener may be added to a subsequent rinse (the neutralizer helps fabric softener function better). Dryer sheets essentially are wax that melts at dryer temperatures to coat and lubricate fabric.

Honestly...I just read a dilemma the other day about slate. I found a youtube...WD40 was the solution. Clean the slate with plain water; let it dry over night; then spray the WD40 and wipe with a clean cloth. I'll see if I can find it.