My pool was recently redone with diamond brite. A stain appeared soon after the fill was started. The workers came late in the day and were working in the dark. They had to string lights up to finish the pool. The mottled areas were done last, right before they exited the pool. I am not happy with these areas and the pool company that did the work is maintaining that it is a result of the fire up. The fire up was done by another company and all instructions were followed. Any suggestions on how this could be corrected or the cause?