My ph is around 6.9; ec is 160 (tds 80) and kh is around 1.5 - 2.0.

I purchased 5 L172a from two very reliable sources and over the past 2 months they have slowly died off. The aquarium is a 450 gallon (8 feet long and 4 feet wide); the water parameter is around ec 180 (tds 90); kh 1-2 gh 3-4 and nitrate near 0. There are fair amount of live plants and large amount ...