Too Much Light For Clam???

[MMAX]

Is there such thing as too much light for a clam? Had my Cook Isl. Maxima as high as I could get him on my rocks a couple of inches from the top of the water and maybe 12" away from my T5s. He seemed fine for a few weeks up there until I found him this morning on the bottom of the tank. Put him in a cradel shaped piece of rock and left it on the bottom of the tank. Checked him when I got home from work and he looked great. I've never seen him opened up like that. Obviously something bothered him to let go and move somewhere else.