sea monkeys died instantly

I am new to taking care of sea monkeys, I only really got them because my little sister bought the Sea Monkeys on Mars one.

Heres the unfortunate series of events - day 3: 5 sea monkeys hatched - day 4: counted around 12 sea monkeys - day 5: 1 sea monkey left - 1 week: they're all dead and their poor little bodies are on the ground

its been almost 3 weeks now and i still stir he water just in case but im losing hope and i think i killed them all - not in direct sunlight - water is not cold, I live in a tropical country but i don't think its THAT warm - fed only on the 7th and 14th day with the yellow spoon

what happened?? :((