I would go ahead and put them in the ground! If daytime temperatures are warm and night time temps go below 55, it can cause it to drop blossoms (which doesn't harm the plant any and it will put out new blossoms). Definitely don't bring them in at night, you just ruin all your hardening off.
I don't know about the flowers turning white. All I can figure is that it is either a sun exposure when they aren't used to it or a reaction to the cool nights. I doubt it is anything to worry about if the plant is growing and the leaves look healthy.
Yes, probably over-thinking!