Yeah, your tank is still cycling so it is not uncommon to lose fish during this time. It takes 6-8 weeks for a typical tank to cycle. If your fish is flashing, that is usually a sign of ich. Do you see any salty looking spots? It literally looks like your fish got dropped in a salt dish. Usually by the time you see this it is too late to save them, but you definitely shouldn't treat things you don't know for sure your fish have.
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Phishie
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"An ounce of prevention is worth a pound of cure."