07 ram 1500 volts low batt and alt tested good

So truck was running just fine and just drove from ft worth
tx to OKC OK and everything was fine. Get home go to bed
and get up to go take kids to school and drop them off. On
my way to work from school check gauges light pings and
volt gauge about 1/4 and normally just past the half mark
sometimes a little higher. Went to both autozone and
oriellys and had battery and alternator tested and both
places said both checked good. I'm at a loss. There was a
little corrosion so I sprayed and cleaned it and my next
guess would be to change the terminal wire from the
positive terminal to the alternator just because the end
looks a little crusty so could that possibly cause this? I
need help. Disabled veteran that works part time and is my
family's only vehicle and can't get into a new one until
August but I can barely make it anywhere as it is right now
so need all the input you go starting with simple fixes first
then work to the ridiculous shit lol. Don't hit me with a flux
capacitor or blinker fluid or it's a dodge or change your
motor I'm serious and need honest opinions not Kevin and
Karen input.