Yeah, your images are way too big. Are you zooming in on them? If so, only make the image size as big as it needs to be on your closest zoom. Make sense?
example: I work in 720×486 at 72dpi. If I have an image and I know that I am going to zoom into it at a scale of 200%, then in photoshop, I make sure that the image size is doubled to 1440×972 at 72dpi. This ensures quality of image without going overboard.
Another tip I would give you is to apply a little bit of a blur to the image. Since you’re scaling it from such a large image, you might experience buzz from the small lines. Just a dab of blur will do, but not too much or the image will go soft.
My 2 cents,
Reins