Which brings up the possibility of a power blip/surge which might have fried the batteries if they were all recharging at the time.
The most common thing I know that will bring down a functioning cell phone is battery failure. Years ago I would always buy extra batteries for my cell so I could ‘pop in a freshie’ when my battery died. When the battery would no longer hold a charge, a common occurance, I would replace it. However, like printers and their inks, all cell phones apparently have a unique, expensive replacement battery so this is no longer a cost effective strategy. If there were some standardization of batteries, then we could buy cheaper aftermarket replacements.