Subject line appearing to others in group sms texts.

When sending SMS messages in a group text, my texts appear with the subject line (Just saying New Message) on other people's phones, but I can't see it. The "show subject" feature is not turned on in my settings, and it does not happen with individual sms, imessages, or group imessages. Also this just started happening yesterday. Can anyone tell me how to fix this? I am using an iphone 6 iOS 9.1