My pleco! URGENT! Please HELP!?

I have a common pleco, and lately he's been loosing color. He still is active at night, and sucking, and eating the algae wafers i give him. But he's loosing color. Is something wrong with him? He always is under my rome decoration, he is upside down possibly hiding from the light. But if he is stressed then what should i do? Please this is urgent!