Question
is it too late to add sulfur to a flowering veg garden? if okay, add liquid sulfur?

Answer
You are basically adding sulfuric acid to your plants..and it will burn them..it should be done in the winter, mixing it into the soil in letting it set over the winter, and then turning it in at springtime with other needed nutrients.  For more information on soil building visit out website:  www.avant-gardening.com