Alternator constantly charging??

[Alexquade]

2014 Sierra SLT. I noticed a couple nights ago as I was getting on the interstate, my fog lights deeply flickered for a second when I turned on my blinker. Noticed it later as I pressed the brakes to slow down also. Looked at my volt gauge and it’s reading BARELY above 14 and hasn’t moved since then, like it normally does. Went get battery and alternator tested and both tested good. Battery had 14.84 v and 100% charged. Alternator was putting out 14.94 v with a/c running. I’ll attach a pic of the gauge to show. I had an 11 Yukon XL that even with a new battery, every time it was tested it was never tested 100%. Always around 80%. Advice?? Bad wire/ground somewhere? Bad alternator?? Thanks!!