It shouldn't be too bright for them there, it's at the back of the house away from any direct sunlight.
We have java moss in there to help with nitrates, quite a lot of it so they can hide if they need to.
I haven't interfered with them at all since yesterday evening, so I'll check on them later on today. (Currently at college).
We have another two tanks in a different window and they seem to have calmed down somewhat, the death rate in those two is dropping where as in the third it still seems to be going up.
I'm thinking it may well be something completely out of our control.