Left to themselves, they pick their own outfit each day — a daily-rotated look that their photos actually reflect. One look per day, everywhere you see them.
The lock
If dressing them is your thing, open their wardrobe and tap the you pick / they pick toggle. Locked, they wear exactly what you choose and nothing else; unlocked, they dress themselves unless you've picked something.
Both modes are one tap apart — it's your relationship either way.