I'm sorry I haven't read this thread until today! I'm praying that Anika's vet will figure out why she is not eating and can help her to get better.
I'm wondering if she might have the Herpes virus? I know one of your other cats has it and it's awfully contagious. Anika could have picked it up with the last break out of it and may not be showing the 'usual' signs of sneezing. Not all cats show all the symtoms but she might be feeling unwell enough to lose her appetite. You could try mixing some of the Lysine you use on your other cats in with some tuna juice and she might show some improvement in a day or two. She might not be up for eating the tuna meat but the juice is usually irresistable.

But with every day that she doesn't eat, it may make things worse. The best option is to get her to the vet but if you are looking for ways to sort through this before having to take her in, you could buy some NoSorb from the vet hospital (it's under 10.00) and it's made up of these little plastic pellets (I think they're plastic ) and you could put her in a room alone with a clean litterbox with no litter in it, just the NoSorb. When she has used the box to pee, pour the pellets and the pee back into the container that the Nosorb came in and take it back to the vet. It's obviously not as sterile as if they did a Urinalysis right from her bladder but if she is fighting an infection, they might be able to detect it in the sample. If she is, they'll ask you to bring her in to get her examined and on the right meds.
I know you are not sure who is doing the peeing and it might be difficult to figure out which cat is doing it. Because she is otherwise unwell, it could be that it is her who is doing it.

If you need more help with the cost of vet tests, please send me a quick PM. I remember offering something way back when but at the time you had things sorted out and I never did get anything to you. I'd be happy to help a bit now. I'm so glad to hear that some PT'rs have been helping. PT is the best!