Is it possible to kill fish with the weekly cleaners and tap water safety agents?

i havent killed my fish nor do i want to, thats too inhumane for me. but could i kill them by using too many tank cleaning agents. currently i am only using the right dose of 2 agents, the weekly one and the one used when you change the tanks water. but i am about to use algae controlling agents in there. could a cocktail of all three in one day kill them?