A Logic Problem Involving Cats

Since around Christmas, Crash has had a severe allergic issue going on. On top of her normal sneezing fits, she's developed really itchy skin that she ends up scratching until she bleeds and she pulls out her hair.

We've taken her to the vet twice, got her pumped full of steroids, she's fine for 3-6 weeks, and then the rashes reappear.

The vet says its most likely an allergic reaction to something. They originally thought it was the Christmas tree, but since it has reappeared, they think its something else.

They haven't found any parasites on her, so its not the most likely culprit.

The next most likely culprit is the food. They suggested feeding her an expensive, non-grain, non-chemical filled food. Don't know if everyone knows this, but that stuff is like $12 for a 3 lb bag.

Crash doesn't eat much so that wouldn't be an issue except we have a fat cat that likes to eat everything.

So this next part is going to sound like one of those logic problems where you have to figure out where everyone sits around a table based on the clues given. (IE, Mary likes to sit at the head of the table, but Sarah doesn't like to sit next to Mary.)

This is a rundown of how I've spent the past few days.

Give Newbie and Slider their normal food.

Give Crash a separate dish while the boys are distracted.

Crash sniffs expensive food and walks over to where the boys are eating.

Slider gives up on normal food and sneaks over to Crash's dish to eat the expensive stuff.

I catch Slider and spray him with a water bottle while he takes one last huge bite and walks off.

Crash will only eat the cheap stuff.

Newbie will eat anything in a bowl. He climbs up on the counter where I store Crash's food and eats from there.

Crash will eat tuna from a can, but that requires me to watch over her eating like a prison guard and shooting the boys with water anytime they come close.

So essentially the two boys are eating expensive food, Crash refuses to eat anything but the cheap stuff and real tuna. Meanwhile I'm having to give Crash "I'll slash your face open for looking at me wrong" Story Benadryl and spray her sores with antiseptic, anti-itch spray.

Why won't they just help me help them?

I was told yesterday that all of Crash's issues could be hormone related as well. A co-worker had a cat with similar symptoms after it was spayed. Which would make sense, because after Crash was spayed was when she started sneezing. So she might need some hormone treatments.

Any other ideas from the internet?