yellow tips on flowering stage on upper leaves

Looks like high ec in the medium. When EC levels become excessively high, the medium's osmotic potential increases significantly, which negatively impacts a plant's ability to absorb water and nutrients. Things get a little droopy when water stops flowing so freely. Worth noting. flushing will wash out nitrate but not ammoniacal nitrogen or organic matter. When growing organically understanding the electrical charges of different nitrogen forms is fundamental to effective organic weed grows, as it dictates how nutrients interact with soil particles, are retained, and are absorbed by plants. Too much ammoniacal nitrogen (20% or over) in a growing medium is harmful and potentially toxic. Everytine you flush you wash nearly everything out but the ammoniacal. Then reapply more organic nitrogen. Excessive ammoniacal nitrogen can contribute to yellow tips and margins on leaves. Flush with 4-5 times more water if you want rid of ammoniacal. Symptoms of ammonium toxicity usually appear first in the younger leaves or new growth areas. In contrast, nitrogen deficiency symptoms typically appear first in the older, lower leaves. Gluck.