Multiple bad 1 year old batteries

I have a 2011 ELXD. Last year I replaced all 9 of the 8volt batteries. The cart was towed to my garage last week. Seven of the batteries had less than 1 vdc another, battery I charged and performed a discharge test. At 75 amp discharge it should take about 70 minutes. It only lasted 5 minutes. Of all of the 9 batteries, only one checks out good. What would cause so many batteries to go bad in one year?

Defective batch
Gross neglect
badly malfunctioning charger

Any one of those could case the batteries to be in the state they are in.

What happened between when the batteries were installed and they were discharged to 1VDC?

Not keeping the acid/fluid level above the plates, preferably properly kept to the proper level iinstead of just above the plates.

Not recharging the batteries fully after use. Ie running them down and then letting them sit for days before charging.

Over charging constantly and usually this requires lots of fluid top-off since there’d be excessive bubbling.

Running the batteries below 50% SOC(~12.2VDC or 2.0V/cell ).

To name a few reasons for “new” batteries not holding a charge. Do any of these sound like things which happened to these batteries?

Batteries are Gel. I was told by operator that they left the cart set for several weeks without charging. I don’t think that would cause batteries to drain this much.

“a few weeks” often sounds a lot like a few months…

Unless the master disconnect is open, the older gems have a parasitic drain even when “off”. Not sure if that ever got addressed on the newer ones like yours, but depending on the severity and time, it could flatline a battery.