A friend has a pond that is getting over run with cattails. We sprayed 24 gals. of ShoreKlean 4oz./1 gal water. Got about 25 burn. We took a step ladder into them to spray, waded and sprayed inside, walked the bank and sprayed it. Sprayed one shore to kill off small willow trees starting. Going to contact the seller RuralKIng. What could we hqve do wrong for it not to work?