It sounds like it started with enthusiasm and now people are tired and lost motivation.
As a leader you are expected to provide that ambience where everybody is having fun, connecting with each other, excited working towards the common goal, not only getting the project done but also building long term relationships that they can leverage later. Also as a leader you need to build that emotional connection with your team, so they open up to you, you build that trusting relationship with them, so they can count on you as a leader showcasing honesty, integrity, empathy, be a role model, leading from the front, be a torch bearer, be a true leader for your troops and of course help them out in getting their tasks done, meaning you don't have to be the master of everything but you need to get them help when they are struggling.
The big difference while being a people manager is that humans are emotional, when people enjoy what they are doing, connect with each other, help each other, the whole result produced by the project team is much more than the sum of the individual parts, and that is the magic every people manager wants to create.
I would identify the reason for this tiredness and lack of motivation,
i) Is it because it is lot of work ? or
ii) Is it because the way the project is being executed in kinda dry, no humor when people get together? People don't like to come to your meetings any more?
iii) It is not fun anymore or people don't enjoy being together anymore?
iv) May be one of the team members is not carrying their load that they are supposed to?
v) I would even have a one/one chats with every team member - Hey I feel like the team is not enjoying the project anymore, what do you think the reason is? something along those lines,
Then address it by getting a solution for the problem you identified,
1 - What is in it for them? What is the win for them at the end of the project? What is that motivated them to take up this student project in the first place? Remind them that is the win and that is the reason they took up that project - May be in the end - may be announce an celebratory party or something, something as simple as a get together, it doesnt have to be fancy, but something simple and exciting. Keep bringing that winning or whatever that made this team take up this project in the first place
2 - Make the meetings engaging - Communicate with a lot of pictures, a picture is worth 1000 words and a story is worth 1000 pictures - Do not make the meetings boring
3 - Make the meetings engaging, tell stories in the meetings, tell stories that students will never forget - Do not let the meetings be a boring drudgery
4 - Emotionally connect with the team members, build one on one personal relationships, shared hardship is the best way to build long lasting relationships, that is why the men that went to war together will be the best buddies for ever. And also people that worked together in a difficult project and made it a success cherish that time for ever
5 - Always use a white board and draw while communicating in your meetings, so people are not bored
Good luck !