Battery power decreasing, and help identify "buzzing" device

I have a 1993 Cadillac Sedan Deville and it's only been a month or 2 since I just replaced my car battery.

Last week, I noticed that my car was a little hesitant to crank after I drove somewhere and parked it for a moment. I did an acid test the next day with a glass tube

that has 4 floating balls inside.

On the positive, the cell nearest to the post measured at 75% and the others were somewhere between maybe 80 -100%.

Then on the negative side, the cell nearest to the post measured having 50% activity and the other 2 were at 100%.

I feel like there must be something in the charging system that's pulling down on my battery.

By the way, there's some kind of a device that makes a sort of a buzzing sound when I turn the engine off and it buzzes for a few seconds. It does this periodically.

If anyone can tell me about the situation with the battery losing it's power and the "buzzing" device, please let me know. Thank you.

I would check the output of the alternator to start with make sure it is charging correctly. As for the buzzing noise, could be the air compressor for the level ride system.

I've seen new batteries out of the box be DOA. Get it checked where you bought it.
The buzzing noise might just be the ISC motor resetting itself. Probably normal.