They may be rubbish I don't know about these particular lenses. Are you trying to focus in auto or manual mode. If they are similar to my Raynox lens then I use f11, 1/200, Manual focus, and diffused flash or preferably off camera flash if indoors or taking anything which moves. If outside in natural light then I dont always use flash, but I find if I use too wide an aperture it is very difficult to focus.
How about putting some examples of your problem on here, along with exif data, then someone may be able to give you more help.