That's a HUGE no in my books. Bleech water I find is dangerous. I would only use it to sanitize pots before placing new soil into it, and in very small amounts. The bleech will not only kill the good bacteria in your soil, but will also go into the plant and whatever produce you are trying to grow.
As for the mold on the chard plants that's something that I would look into. Vinegar water does an okay job, but again you risk damaging the plant. Have you tried Neem oil?
Is there anyone else you could talk to about the person selling produce with mold?