No doubt about the over-fertilization problem, leaf-curl downward says that to me, your growing hydro and you have to be completely on your game with going hydro... I have done the hydro way and I still find soil the best way to grow. Hopefully you'll go the soil way next time around. The keys are good soil mix, right fertilizers and CO2 as much as possible, that is the reason that soda water is good because of the CO2... but don't spray it on any plant that in flowering, try to find like a place that sells CO2 tanks, about $100 or so, you would be better off putting that into your grow room and release a little at a time... like for 2 minutes then again a few hours later...a filled tank should last you about 2 weeks and the results will please you... If you need a list of recommended products, i would be happy to help answer any of your problems... flush your roots until you see your leaves turn a lighter color, then cut your nutrients flow in 1/2... it should be enough to get you through your cycle... then go soil
Alan @ ABC