sorry about your loss.
IMO way to much to early. you should have snails and 1 fish ( two tops ) at this point, if even that.
a tank can cycle, yes. however its only going to build up enough beneficial bacteria to support the life within the tank. for example, if you only have one damsel, your tank can support one damsel. this is why going slowwwwwww is best so you can give your tank time to mature, stablize, and culture these good bacterias.
the tang and 6line were prob. just investigating each other then as it was a new addition.
i need EXACT water parameters. ammonia, nitrite, nitrate, pH, temp, salinity, flow, alk, cal and mag please, also what you are using to test for them. thanks.