Giant Rainforest Mantis (Hierodula majuscula) turning slightly brown?

[mossymantis]

All three of my Hierodula majuscula nymphs have become slightly brown, specifically their eyes and their heads have become very slightly tinted. One of them is L3 and the other two are L2. I thought the eyes might be because of light exposure, but they stay the same shade of slight brown no matter the time of day. They were a light green before.

Does anyone know what might be the cause, and if there's anything I can do? Is it just related to molting? Or perhaps it's just a detail I hadn't noticed before... it's pretty subtle

 

[River Dane]

Mantids can occasionally change color after molting, although no one can agree on the specific causes. 

However, it could be a sign of illness if they both turned th same color and have different habitat colors. I sugges  posting some pictures.

 

[mossymantis]

Mantids can occasionally change color after molting, although no one can agree on the specific causes. 

However, it could be a sign of illness if they both turned th same color and have different habitat colors. I sugges  posting some pictures.

Thanks, I'll try to take a picture tomorrow when there's better lighting. I'd originally considered adding pictures but unfortunately I don't have very good "before" pictures to compare to