Is there any information about what temperature should be maintaned to keep whites from getting yellow. I would prefer to grow them cooler now and not have to hold them at a low temp later.

Different varieties of whites are going to respond differently to lower temperatures. Our advice would be do drop your temperatures as you had planned but if you notice the whites becoming to creamy are turning greenish to turn the temps back up. Growers are also using Fascination right at finish as a spray targeted a the bracts at the rate of 2-3 ppm to whiten their whites. This might something worth trialing........