Nothing to worry about, it's normal and your body will bring it back up when it needs to.
Each person is different, follow the nudges and you should be ok.
An occasional dip below the zone is common. If your line regularly goes below the zone and stays there and you feel fine, that is normal for you.
You may possibly need to increase your protein as a source of energy for the body and for muscle repair and recovery.
If you follow the nudges you should be ok.