"Too low difficulty" is a message from the pool to the miner indicating that the miner submitted a hash which did not meet the minimum threshold of acceptance set by the pool for that specific worker at that specific time.

Some pools constantly adjust the minimum setting to control your slice of their bandwidth while other pools just set a certain minimum(say 4081) to connect to the pool initially then allow your worker to adjust to a lower setting(like 416) that's appropriate for the device. This helps filter out CPU and GPU miners which just can't really cut it anymore.

The miner needs to restart "work" if the setting changes at the pool. Before it resets, it will continue to submit whatever is valid because at the time the hash calculated is considered valid by the miner. Remember your device may have 1,2,16 ASIC chips but each chip has hundreds of cores, each core is trying to solve and submit a hash of the same equation until its instructed something new. Your terminal can't show you everything, its more of a rolling summary, different levels of logging can be used to see a deeper analysis of events.