Battery info

[Wake_rider]

Hey all. New member here and I hope this is the right place to post my question about my new Trojan t-105 batteries on a 2006 TXT 36v:

10 days old, I've run them and recharged every day. "H1" stamp (August 2021 ship date, I believe) -

After charging, I'm only getting 37.0v. I just put a multimeter on each battery and this is what my readout is:

Battery 1 (closest to positive wire to controller) - 6.32v
Battery 2 - 6.31v
Battery 3 - 6.32v
Battery 4 - 6.03v
Battery 5 - 6.03v
Battery 6 (final battery connected to negative terminal to controller) - 6.04v

I have the ground wire from the charging port going to the negative of battery 4. Is this my problem? It's not really long enough to make it further. Or is this a bad 4th battery that's not letting higher voltage get to the last two batteries (5 and 6)?

Sorry if these are ignorant questions. I'm from a motocross and offroad vehicles background and this is the first time I've ever really messed with anything electrical beyond replacing parts. I'm not experienced with this stuff at all but am willing to learn.