If your plants are on the windowsill, close to the glass, it's possible that they're getting too hot during the day, or too cold at night. If you think heat might be the problem, you can reduce it by increasing the airflow around the plants with a small fan. Moving the plants about 6 inches away from the glass can help resolve either situation.
While aloes can survive drought conditions, they will struggle and won't look their best. It is important to let the soil become fairly dry between waterings, but you don't want to overdo it. What size are the containers, measured across the top?
"Isn't it enough to see that a garden is beautiful without having to believe that there are fairies at the bottom of it too?" - Douglas Adams