poor photo quality in pages

I have a document in pages that's about 6 pages long; I've inserted several pics into the document and notice the quality of the photos continuously toggle from the original quality (good) to a much lower blurry quality (bad). When I use the "enhance" button in the image menu, it corrects the quality back to original, only to have some other photo in the document degrade in quality. Any ideas on how to get ALL photos enhanced without losing the quality? Thanks.