Will Flourish Excel kill fish?

I have terrible hair algae boom so I decide to over dosing Flourish Excel to kill them. Actually, this is my first time using the Flourish Excel. I got it last night and put 25mlx3 in my 55gal tank. This morning, the hair algae does look thinner and this is a good thing. But I notice the platy and cat fish looks weird after I add the Flourish Excel. They just don't move that much. I even suspect they are dead. Should I do water change ASAP or just let them sit in until the hair algae get controlled?