too hot (location dependent), too dry, too wet, not enough light - those are the most common indoors problems. Perhaps one of those. Any more details about your set up or watering?

BTW - does this container have holes/drainage?

FataMorgana

They are in a little room, I put the fan on for about 15 min twice a day and its about 20 C. The lights are about 4 inch above the plants, the plants come dry easily so I water a little bit every 3 days and yes they have a good drainage.. thanks for you help