I would use Mac’s play without amplification suggestion and see if the E and B strings still have lower volume. If they do before buying anything else I would change strings keeping the same gauge but maybe a different brand. I have had the same problem with some packages of strings, i.e. for some reason the E and B strings were DOA out of the package.

You didn’t say what gauge or brand of strings you are using but I have heard the same problem on many of my students’ guitars, acoustic and electric, when they use ultra-light strings 8s, 9s or 10s. Maybe the next gauge up will solve the problem.

Older strings have a propensity to exhibit the same problem, especially if you don’t wipe the strings down after every time you play. Could that be the problem.

I hope this helps and good luck.

I think my wife has started to show the first signs of dementia.
She said she can't remember what she ever saw in me!

64 bit Win 10 Pro, the latest BiaB/RB, Roland Octa-Capture audio interface, a ton of software/hardware