Adding molasses to your airated reservior is very benificial. It breeds effective microorganisms that are essential to your plants survival. You want to wait 24 hours after adding about a tablespoon per five gallons. The frothyness on the top is actually a good thing it indicates the pressance of the organisms. As long as the nutrient solution does not smell stagnent it has aerobic bateria in it. the sugar doesn't feed the plants; It feeds the organisims that feed the plant. There is much research online to the truth to this amongst other places. In the case of the dropping leaves, The ph...Sugar can change the ph of your water, making it more alkaline so you need to check and correct before you water. Also if you read the nonplant food ingredients on many nutrients one of them is sugar cane extract. Sorry about grammer and spelling it never was one of my strong suits.