Calathea problem

Hey guys,

I'm traveling for a few weeks and my boyfriend is taking care of my calathea plant for the weeks I'm away. He's having a bit of trouble though, three leaves have died and turned both yellow and brown. (find a picture below)

He sprays the plant every morning, it had enough light, he makes sure the soil isn't dry and he's got a humidifier on too. 

Do you know what might be the problem?

Thank you!