Quote:
Originally Posted by
werra 
Not all my cats have that stool color I checked the litter box yesterday. There is a stool there that is brown color but I don't know who among my cats...
Well, the first task would be to determine who is depositing the green poop. As cats (generally) make at least one deposit daily, it could take only a few days to find the perpetrator...but, you'll need a second litterbox and a separate space with food and water where you can isolate each cat for a day.
Now, speaking of litterboxes, if you have four cats and only one litterbox, you're fortunate if they haven't been doing their business outside the box. There's a rule of thumb about one box per cat plus one extra, but you might not need to go that far. More info here http://www.catinfo.org/?link=litterbox#Types_of_Litter_Boxes,_Size,_Number_and_Location
We'll both be in trouble if we get too far into the food discussion here - this is the health forum - but, in terms of food and general health, wet food (almost any wet food) is a healthier choice. Here's why http://www.catinfo.org/#My_Cat_is_Doing_Just_Fine_on_Dry_Food
You asked about using Iams dry 'for now'....if you are going to change dry foods, you need to do it slowly, over a period of several days/a week. Mixing both, gradually replace the old with the new. Otherwise you'll upset the digestive systems leading to other litterbox problems.
You haven't said whether the green poop appeared just after you changed foods or while they were on Orijen.