Taste it after 5-6 days for diacetyl. If you're sensitive to it, it'll show up then, I wouldn't wait two weeks to check on it if you feel the need to check at all (it'll be too late if you wait two weeks). The dunkel I have in primary, I was concerned about since I didn't see any surface activity in my carboy after 36 hours or so, I only had the slightest movement in my S-airlock. The surface of the wort/beer was clear, no krausen or anything. I gave it a swirl (one swirl mind you), and the airlock exploded. The next day I had a nice 1" krausen, which is about the most you'll get IMO with a proper temperature lager ferment. If you're seeing something, that's just fine, and I bet it's progressing fine.
I have used gelatin before, but after a month+ of lagering, you probably won't need it. I've used it on some English ales in the past with good results. Never needed it for a lager (yet). Let it lager before thinking about gelatin IMO. Cross that bridge then.