I have cats: a male 11 1/2 years old, a female 5 years old, a male 3 1/2 years old and two little girls aged 15 months. Four of the cats (the four younger ones were all strays that I brought home. I had always given my cats wet food with a large feeder of dry food at the side.
Recently they stopped eating the canned food so I changed the flavors, brand, etc. They eat a little bit and leave the rest. I started alternating dry food with wet food. When it's a new bag of dry food, they dive in and eat like crazy once or twice and then walk away.
I keep changing their food but nothing seems to work and I am afraid, though none of them look underfed, that they are not getting enough food.
Any help will be appreciated.

Try buying a can of "Jack Mackeral" at your canned meats aisle in the grocery store. The strong odor will attract most cats. It's what I give my cats when they have a cold. Also, the cheap store brand food is very attractive to cats and dogs, as again it seems to have more odor.
You can also try wet doog food. My cats love to lick the gravy and even eat the slices of meat. It is such a problem at my house, that I have to feeds the cats first, then I can sneak the dog food out to the dog while they are distrracted.

Forgot to mention...
If this does not work, then you should consult a vet. There may be a physical problem. But sometimes they are finicky eaters. Not my brood, they will eat rice, cheese, baloney, anything off my plate!

I thought of that but they are all so active and playful that I seriously doubt that it is anything more than being downright stubborn and finicky. Thanks again!

I meant to ask you: do you feed them the mackerel by itself or do you mix it with wet food? I will be buying it for them tomorrow!

I won't give you a disagree BIGBOPPER but I do. Cats shouldn't be fed dog food, it doesn't contain taurine like cat food does and it is an important part of a cats diet, without it, it can make them very sick and eventually die.

I meant to ask you: do you feed them the mackerel by itself or do you mix it with wet food? I will be buying it for them tomorrow!

Try feeding it to them separate of cat food. If they eat it, maybe tomorrow blend some cat food into the mix. Eventually you will get them used to cat food.

I won't give you a disagree BIGBOPPER but I do. Cats shouldn't be fed dog food, it doesn't contain taurine like cat food does and it is an important part of a cats diet, without it, it can make them very sick and eventually die.

I don't feed my cats dog food exclusively. However they have a habit of trying to eat it when it is time for me to feed my outdoor dog. I am suggesting that a strong ordored food will whet the appetite of a finicky eater. Animals use their sense of smell more than we do, when it comes to dinner.

Sorry, I partially misunderstood your answer, I thought you were saying just to give them dog food and not cat food :)

I really have no intention of giving them dog food. They have already demonstrated that they will not eat dog food. When my dog was alive, they were less than interested in her food, but thanks for the suggestion!

Sorry, I partially misunderstood your answer, I thought you were saying just to give them dog food and not cat food :)

Not a problem, I just know from experience even with myself, that odor plays a role in taste, and attractiveness in food. If you have a cold, everything tastes different partly because you can't smell it. Well for animals that are bored, sometimes they need to smell something stronger than what they are used to.Nutrical will also stimulate appetite, but it should never be used for a meal replacement. You can find that at a pet specialty store, like Petsmart.
If the cats are not eating anything at all, especially after Jack Mackerel, the OP might want to take them to a vet.