I agree with this. The key in the jar was fine, I had no problem with that. The one in the frogshine room was okay too. The one I had an issue with was the one in the room with the frog lady, since I was coming in from the back door each time I managed to miss it on 4 or 5 passes through because it doesn't light up well from that angle. I'd advise adding a little sparkle or something to collectibles.
Speaking of items, I couldn't find the vinegar, is it actually in the demo?