Firstly look at your watering. Once a week is a timetable. Plants don't need that. They need water when they need water, not to a schedule. Secondly filtered light may be insufficient.

Alocasia are tough to over water (mine actually lives in water) and once a week might not be often enough, especially if it's hot. Without seeing more pictures it's really hard to tell what's going on but it does sound like you're plants are potentially thirsty. You definitely need to water by soil feel rather than on a schedule. Also, move closer to a window, all of these plants are going to need the brightest light possible but no prolonged sunlight touching the leaves. Filtered light isn't enough.