It seems clear to me that you need to talk to the senior author who actually did contribute and see if they can talk to the other two. You wrote that "one of the authors said that they were experts who are so great (bla bla)" so it sounds like it wasn't really your choice to add them in the first place.
Let's call the good author G. Let's assume G actually cares about your career (e.g., wants to keep working with you in the futute, wants you to get a permanent job, etc.). Then, G should be receptive if you TACTFULLY express your concern to him/her that the paper won't help your career as much with 4 authors as it would with 2. While you feel like you haven't seen any "substantial" contribution from the other 2, it is always possible they have been communicating with G and that some of G's contributions are in fact due to them.
If G agrees with you that the contributions of the other two don't warrant authorship, then G can fight this battle on your behalf, rather than having you try to signal it some way in the writing, which is most likely going to come off looking petulant and unprofessional. If G fights the battle on your behalf, you won't face the professional consequences you fear.
It's also possible that G won't be able to get them off the paper. In that case, G can still soften the blow by giving talks that state that you did most of the work, and writing the same in letters of recommendation for you. At all costs, do not alienate G.
For context, in my first paper, I invited my advisor to be a co-author because he'd made substantial contributions. He declined, telling me that I needed the paper more than he did. I still put a huge acknowledgment to thank him for his help. I have since paid this forward, sometimes helping people a lot but not ending up as an author (especially post-tenure). That's how a good field should function. If G is good, they will understand this and find a way to help you be successful.