You can usually tell by thinking back on how well you took care of your baby.Did you manage to keep the Happy and Hungry hearts full for the whole hour?
If they emptied - how many were empty and for how long?
As far as Healthy Adults go... actually the Kuchipatchi is usually considered one of the more healthy characters - not as healthy as Mametchi/Mimitchi, but nevertheless....
By healthy, I usually mean I got the character by keeping the Happy & Hungry hearts full most of the time - playing Games more often than giving snacks to fill the Happy hearts and getting a training point score higher than average - say, 7-9 out of 9 points.
I usually find that the Healthy characters don't empty Happy hearts as quickly as the weaker characters. They also brush their teeth every morning and evening.
When they connect and play a game, as they shoot up off the screen to begin the game, healthy characters normally show a little puff of cloud. The weaker ones tend to show squiggly lines similar to the lines you see if they are about to go to the loo