Continuity mistake: When Silas is painting the wall green, some parts jump from being painted to unpainted between shots.
Other mistake: When Andy pulls his piece of meat out of the fondue pot it hasn't been cooked at all. The fondue obviously hasn't been turned on (in the next shot he sticks some meat in his mouth, which has been cooked and is smaller).
Answer: It's not uncommon for TV shows to suddenly "age up" baby/toddler characters in order for them to have more narrative purpose. Other examples of shows I can think of that did this are "Step by Step," "Last Man Standing," "Boy Meets World," and possibly "Dexter."
Phaneron