I'm sorry to hear about this issue Leann. I'm Linda, a vet with 10 years of clinical experience.
Most often, indoor soiling and spraying like this will be a sign of anxiety or stress, usually from sharing reosurces and living in a multi-cat household.
For some, underlying stress can lead to cystitis (bladder inflammation).
It is also worth considering that any soiled spot becomes a 'magnet' for others, who will want to then mark their own scent.
With 12 cats, it is a difficult take to keep them all content and feeking secure.
Most cats have a preference for being lone rangers and enjoy their own space.
They dislike sharing litter trays.
In the ideal worls, we have 1.5 trays per cat. With 12, this will likely be difficult (depending on available space). The more the better, and I'd have a variety of types e.g. top loading, ones with a larger bottom etc.
Trays should be in quiet areas of the home with low foot traffic.
Anything that is soiled must be cleaned ASAP with an ezymatic cleaner to immediately remove the odour.
To help reduce any stress or conflict among the cats, it helps to:
It is worth saying that any 'repeat offenders' should have a medical exam, so we can rule out e.g. urinary crystals or an infection.
