Short answer: Yes, Jain munis are generally not supposed to speak at night according to traditional conduct (moolachar). They focus on meditation, study, and quiet reflection during the night, and speaking is typically avoided. There are very rare exceptions only under strict guidance (e.g., for necessary blessings or urgent situations), but the standard rule is silence at night. This principle aligns with the broader Jain emphasis on ahimsa, restraint, and disciplined conduct in the dark hours. You can read more on the night conduct for munis here and a note specifically stating "They do not speak at night" here