The group was performing for STARLIGHTs in Mexico when Ravi suddenly collapsed on stage, sending not just fans but the members into shock. In the video below, you can hear Ravi coughing from the beginning of the song before he collapses and N reacts immediately, picking him up and leading him toward where a staff member comes to aid him.
Later on, Leo was also absent from the ending of the show. N reassured fans that both Leo and Ravi were all right. The organizing company stated that both Ravi and Leo had suffered adverse affects from the high altitude in Mexico that they weren't used to in Korea. According to fans, neither Leo nor Ravi were present at the VIP events afterward because they were resting.
Hopefully both of them get better soon!