Hi Neetu,
I would suggest to make a thorough analysis from start (hire) to end (exit) and try to know about their work procedure (how they are working, are they happy with the current responsiblities or manager, etc) or how they feel about the facility,night shift benefits (Free night food, Free transportation,etc), if any and then go and talk to them.
Try to get their confidence that they are same like others who works in day shift. Arrange some competitions, reward them, publish it through your company communication channel, once in a 3 months or 6 months arrange a meeting with company seniors, etc. If we motivate them then the trust will increase.
If you don't have any HR at night then conducting a survey is a best option through which you can get their issues, comments as well as work satisfaction level. If you want to make a shift then you can keep a work tracker in your team folder (which is accessible by all 15 members) in which all 15 member's task should be covered with progress status or comment. It will help other team members to get the exact status of the issues, if any.
Regards,