plant fertilizers and pH

What fertilizers, how much and what are the water parameters you're adding them to?

For every day occurances and dosing...none.
 
Calcium and magnesium supplements will increase the hardness (GH) directly depending on the quantity added. Most will have no effect on hardness.

All will boost the TDS a bit, again quantity related, but with ordinary supplements it is a very small effect which would depend on the sensitivity of your measurement to be able to read.

Any carbonate/bicarbonates added with boost the KH and the pH will go up in proportion.
 
Phosphate (PO4) is the only nutrient that I can think of that affects pH. Phosphate raises pH by bonding free protons making the water more alkaline. Phosphate adds to the effect of carbonate hardness but does not directly show up in a KH test. IIRC, 1ppm is approximately equivaltent to 0.5 dKH. Unless you're a pro and rolling your own macronutrient mix then you probably will not be dosing Phosphate separately. In any case the dosing concentration is so low that you're not going to see the effect in a standard test kit.
 
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