Is it in a small container? they some times spend a lot of time trying to walk through transparent walls, possibly to get to a more favourable looking spot like a patch of sunlight or the like?
They cannot percieve glass or plastic and try to walk through head/eyes first and rub the surface off, imo this is what causes the majority of this kind of damage. A larger container or different material should help, if it ceases to keep rubbing them they may well heal up
Nothing to do with diet Morph, imo its a physical damage caused by rubbing the ommatidia either lightly damaging them as in the cloudy, small amount of damage per lens, this can lead to a more apparent damage, especially in the fovea region, leaving a black "hole" (not really a hole but dark a lack of camouflaged pigmented surface, its been rubbed off and or can be worse as in those those with liquid leaking out)
Notice the damage is in the front part of the eye, the bit the mantis rubs and wares when trying to walk through a transparent but solid object.
When they are active, hungry watch them see what they are doing.
Obviously the one in my pic is right handed :lol:
Edit, the damage can best be described as lightly sanded as in a bit of ply, the layers can clearly be seen
