It looks like everything grew. So either your competent cells are already resistant to the antibiotic (although if it really is DH5b then it should not be) or the plates did not have any antibiotic in them.

Michael J. Benedik Thanks for your valuable input. I will freshly prepare kanamycin plate next time when I do my cloning and see if the same problem happens.

Also be sure to do some controls such as competent cells alone as well as a positive control.

Are you trying to express your protein of interest? In that case, you might need to use BL21 or some other expression vectors. DH5a in not a protein expression vector, so your pET28a containing the gene of interest might not get expressed, thus everything is growing on the plates!