No problem charging them both together or seperately.
There is an argument to charge together as they will discharge together, but, because of manufacturing tolerances they will almost certainly last a different time (although similar) so perhaps consider charging seperately.
Bottom line is if the green light goes off quick they are either fully charged or there is a problem somewhere!!
OK, one battery is charging and one isn't
not happy
will leave overnight and see what happens
Something seems amiss, that should not be the case, have you checked all the