Cat's Spraying

I need some help.

My two male feral Tuxedo cats, both neutered, have been spraying on my silk curtains. I tried Felaway, and that didn't work. It's horrible.

They are both indoor cats, only allowed out during daylight hours on the weekends. Lately they have just gone crazy. They are both 3 years old.

Most of their crazy behavior started when I began leaving an extra bowl of water with a pinch of himalayan salt out for them. We were so pleased at how much more active they were, sleeping far less, and racing around the house like little maniacs. But they also seem to have gotten more aggressive. We have been bit a few times lately, and growled at. They are both doing this.

What in the world do you think is going on here? They are both incredibly health cats, and I don't think there is any illness.

What can I put on my curtains to stop this behavior? I have some cayenne pepper spray, do you think that would work? I don't want to keep having my curtains cleaned.

Thanks.

Molly