I got a batch of Crystal Black Shrimp for my heavily planted nano tank after it had been cycled and the water parameters were perfect. The shrimp did great for over a week as I was slowly introducing fertelizers. Seachem Iron, Potassium and Flourish didn't seem to bother them at all. This morning I decided to dose Flourish Excel and within 3 minutes, all my shrimp started swimiming aimlessly and just sank. I'm convinced that Flourish Excel poisoned them. Any thoughts?