Loose stools, clear substance down legs, and blood in either vomit or diarrhea

My cats were just at the vet 3 days ago for a checkup and vaccines. Everything was good except slightly elevated kidney levels the vet said switch to a food with less protein or renal forumula but the vet food is too expensive almost $80 for a tiny bag! I had been feeding blue wilderness mature forumula dry food. I switched recently to weight loss formula as it has the least protein, I was looking into blue dry food as that has even less protein than wilderness. My other cat has been doing fine, my older cat has been very sick. Today she had loose stools twice covered in mucus, a clear, sticky substance near her pee hole running down her leg, but it "could" be from the butt area before, and now what looks like severe diarrhea or vomit with blood in it. If this is from the food I'm switching back but not sure about the kidney issues how to fix it? Second, she has a very sensitive stomach to begin with and blue wilderness adult had the best results agreeing with her stomach, so I'm worried if she can't handle other brands/formulas? I'm also wondering if her vaccines did this or if this all is something else besides food change or vaccines? Here are photos

Diarrhea or vomit? I see blood

Really hoping that is from the rear end and not the front. Your cat is having some nasty digestive upset it looks like. 

You say elevated kidney values- so did your vet diagnose your cat with CKD? If so, what you really need is a low phosphorous diet. The food should not cost $80 for a little bag, try at a different vet's office or look online. There are some non-prescription foods that can help. 

CinqChats said:

Really hoping that is from the rear end and not the front. Your cat is having some nasty digestive upset it looks like. 

You say elevated kidney values- so did your vet diagnose your cat with CKD? If so, what you really need is a low phosphorous diet. The food should not cost $80 for a little bag, try at a different vet's office or look online. There are some non-prescription foods that can help. 

Click to expand...

I'm not sure what end it was from its hard to tell I didn't see it happen. For now I switched back to the old food to see if she improves, to rule out something else going on.

The vet told me too much proteins, but what you said makes sense. I was recommended Royal canin renal formula, however the reviews say many bad things about it plus all the corn and grains, like science diet in the past, I know won't agree with my cats stomach. I'm trying to find a food like in Blue brand that will be good as my cats like the food and it's good on their stomach.

On Monday I switched to the old food. Tuesday my cat seemed almost normal with slightly loose stool. Yesterday I came home to find twice as much diarrhea all over, I'm thinking all this is diarrhea and not vomit. I don't know if I overdid feeding her I fed her normal amount of food and she ate it all, mabye her stomach still was irritated so it caused this flare up again? If it's still happening start of next week I think she has to go in the vet, I'm not sure if it's the food doing this or something else causing it now?