With Mapnik, not all zoom levels are updated / rendered at the same time. So recent edits can show on some zoom levels but not others.
But they will all be updated soon, probably within a few hours. So just wait a while and your edits will appear on all zooms.
Its also possible that you are looking at a cached copy of the tiles, worth trying a shift+refresh in your browser.
Also, if you don’t want to wait you can mark tiles as “dirty”, which will cause them to be rerendered. To do this, add /dirty to the end of the tile URL.
See this page for details: http://wiki.openstreetmap.org/wiki/Slippy_Map#Mapnik_tile_rendering