This set of posts from the FAQs can explain alot about candy critters.
https://www.fairylandgame.com/fbfairy/forums.php?tid=159225 Yes, there is a different sequence (and potentially different color set) for each type of critter. You'll want to take notes/ make a chart to remember what you have spotted with each shape and color. You can change the food for any set of critters to see if any of the shapes work to bring in other critters. You can also move the shape positions to see if they will be useful for other critters. I started out a bit random, but after they added violet and rainbow critters found it was easier to get through the set of a critter by sticking with the shapes I had and trying to find the color of shape needed. Before I would shift to the next critter, I would try new foods out. Then, I'd go with the next critter that I had the most correct shapes for.