[cem] Using CEM due to post-randomization dropout

Hi, I have a few questions regarding using CEM on an already randomized sample that I would appreciate any help with. Briefly, I conducted an online experiment in which we randomized respondents to 1 of 3 conditions. After exposure, some respondents dropped out before the final outcome measures. In total, I have 417 respondents who completed the full study, but because of the drop-outs, there is unequal distribution of some key variables between conditions. My questions are: 1) Would CEM be an appropriate solution to an unequal condition problem like this? 2) Does the use of the method invalidate the randomization? 3) Is there any literature that uses CEM in an already randomized sample? Thanks in advance, Alisa