Food for various aged cats

Question
Hello, I answer questions on Lost Cats here but was wondering about my 4 cats of various ages and what best would work to feed them all.  They are Bonnie (11), Olive (9), Lucky Streak (fat budda belly 4), and little Sandia (1 1/2).  All rescues ALL very loved, bowls are available at ALL times.  Bonnie came to me with Science Diet for Over 7 years old and her and Olive like this (well so does Lucky Streak).  Then Sandia came into our mix, and she is allergic to all Iams products so we went all natural.  This works fairly well, but when I bring in the over 7 year old food, Bonnie and Olive seem to miss it and eat better.  My Vet recommended Eco (I can find at feed stores) and wanted your thoughts on this natural brand for their wide age spans.
Thank YOU for helping others here as well.  NO hurry on answering, as I'll spend Christmas through New Years traveling back home.

Have a safe and blessed Holiday Season.

Answer
Since you are feeding free-choice to several cats, I would
stick with one brand that they can all eat for your own sanity. While Bonnie and Olive do enjoy Iams when you give it to them, remember they are not human and do not "miss" it when it isn't there. If you gave a cat one kind of cat food her whole life, she would not comprehend that she is missing out on
caviar, tuna, etc.. See? We have to think like a cat

The #1 illness in our country for pets and humans today is obesity. THerefore, me and my vet like senior brands
since they tend to have less calories (less activity, less food needed) Todays housecat does not need as much food
as we think (neither does the average person  lol ;)    )

As long as you don't have a kitten or pregnant cat in the family, a senior diet is suitable for "maintenence of adult cats" as you will see on the label.

Since you like natural brands.. many cat owners feel that
Nutro Natural Choice is THE best food with only real meat
in the ingredients and no byproducts or chemical preservatives. So for you.. I would try out the senior
version of this product if one or more of your cats tend
to get pudgy (which may happen when feeding free-choice)
I think if you view the ingredients on the label you will
be impressed.  Also..its easier to find as I know Petco and Petsmart both sell it  You can visit their website
and learn about their company and how they have an outstanding reputation whereas I've heard that Iams does
harsh animal/lab research.   (no I don't work for Nutro LOL!!)

My PERSONAL favorite is Purina One (I think they've introduced a new natural line).. the cats easily love the taste, real meat is included..and their coats were
shiny after a couple weeks I just had this energy that
they were responding well to it  ( don't work for them ei ther LOL!)  Its about comparable to Iams

http:///www.iamscruelty.com <- this web is written by PETA which in my opinion is borderline radical at times
So read the article if you choose to with an objective mind

Ultimately, the decision is yours..and remember as they say, you could buy the perfect food for your cat and if they refuse to eat it, it's useless!

Also, choose a company that has been around for years and risks its reputation to provide quality food for your pets.

Hope this helps!