Usually dry leaf tips indicate overwatering. They like to be moist but not really wet, and well-draining. As far as the air being too dry, I live in the high desert and I have ten young cacao trees, at least twenty seedlings, and several mature blooming (5+ years old) ones, and although the humidity is a bit higher in the greenhouse, it never gets over 50% all summer, and I would imagine that Vancouver is plenty humid enough.
The other spots MAY be due to too much fertilizer. What are you feeding the kiddo? I usually use very little fertilizer on the seedlings (I dose them about like my orchids...).
The older leaves tend to dry out in general, and the newer leaves look good, except the one I see with a dry tip, so I would just let it go, but keep and eye on the watering and fertilizing.
Cheers,
Carolyn