Give your heroes and villains a reason to say or do something, especially if that something is out of character for them.
“I read Chapter 4 of your story and your MC has always been very tolerant on the topic of religion, yet in it he makes fun of a Jewish boy; why?” – if you get a comment like that then there’s a chance you should edit Chapter 4 or add an explanation in Chapter 5. And I don’t mean write an A/N in Ch. 5 that goes “My MC was having a bad day and took it out on the wrong person in Ch. 4; they are still respectful of other people’s religion”; you should include the character having an off day in the chapters. Go back to Chapter 4, rewrite it and show us your MC is having a tough time. Then, in Chapter 5, have him be remorseful or even resentful of what they’ve done, maybe make him look for the Jewish boy so he could apologize.