i had a brilliant moment of "a-ha!" you mentioned there was baking soda in the water? THAT is your culprit, sure the yeast and sugar probably had an effect, BUT! the baking soda is the main issue. i haven't checked this thread in awhile, but it just suddenly clicked.
baking soda is VERY alkaline, my guess is using that water ramped up the soil's pH to a ridiculously high level. flushing a few times with pH stabilized water and i mean heavily flushing so that you create a good bit of runoff should/could balance things out. you just created the ultimate nutrient lockout basically, with that highly alkaline baking soda.
again, haven't checked this thread in awhile, sorry if thats already been touched on. i just remember that vinegar is poor mans pH down and baking soda is the pH up equivalent.
Shack