Sudden 50% drop in twin battery charge

Sudden (from one 5 min status to next 5 min status) drop in battery (2 batteries) charge from 86% down to 31%. One battery flashing all lights, other battery has one light and flashing other light. Is this a battery death? The drop in charge is roughly about that of ALL of one battery.

On the mobile app, click on the battery icon on the home page, then click on "more information" just under the battery to get individual battery SOC.