The update on this one...
Both jars failed to turn into kefir, after 24 hours.
The regular whole milk was just a soury milk, probably because of the kefir I added to it.
The Jersey Milk developed a bit of yoghurty texture on top, along with milk fat, but still not kefir.
Gonna give them a few more hours and that'll be it.
Next time I try to make kefir, I'll just use kefir grains 😄