If you include the EXIF we could probably help you more. Try uploading them to flickr and then link to them in TP. (In Flickr Just copy the BBC code under Share and then paste into TP)
Vince, were these hand held or on a tripod? Reason I ask is that the iso is 1600 and that, combined with being hand held will be a big contributor to softness. If on a tripod, there shouldn't be any reason for the iso to be that high and, again, it contributes to the softness. Als, your aperture is very wide at f4.8, macro photography gives a very shallow depth of field.
Set your iso to 100 or 200, stop down to around f16, use a remote release if you have one and consider using manual focus as that tends to be more accurate when doing macro.
Ah, macro filters are something I never got on with. I know they're a cheap way to get started and I bought some off ebay at first but could never get a sharp image out of them. Try again with the iso turned down and the aperture stopped down to around f16 Im sure that will help. Also, turn the VR off if you have it.
Extension tubes are another option although I have never used them, I just went out and treated myself to a macro lens.
Many thanks for you help, I will try that at some stage tomorrow, I think I need to search for a macro lens !!