Move them up gradually. They both look like crocea clams, which need alot of light, but don't take them from the bottom right to the top. They need to slowly be acclimated to more light.
From the article I linked to........"When choosing clams, also try to remember that crocea and maxima clams are more light needy than the other three types and will require placement higher in the tank. Clams also require more light in relation to the amount of color in their mantles. Using this as a guideline, an educated reefer will remember that the beautiful ultra or electric grade clams will place much higher light demands on your budget. Browning out of the mantle is an ominous sign that commonly is related to the age of the light bulbs being used in the tank or the type of light itself. In addition to this, look for rocky over hangs or coral growth that is shading the clam from the penetration of light into the water above the clam."