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It may be going dormant. It may also need more water. Do not allow the soil to dry out. If it is drying out between waterings, you need to increase the frequency of the waterings. This article may also help:
https://www.gardeningknowhow.com/ornamental/bulbs/calla-lily/yellow-calla-lily-leaves.htm

Some varieties of white calla lilies will fade to a light pink as the blossom ages, so it is a natural and normal thing.

This article will help you: https://www.gardeningknowhow.com/ornamental/bulbs/calla-lily/drooping-calla-lilies.htm

This could be one of a few things: There may be a pest, such as mealybugs, aphids or mites, attacking your plants and sucking out all the nutrients. Check the foliage thoroughly for any insects or eggs. If you spot any, treat the plants with neem oil. Here is more information: https://www.gardeningknowhow.com/problems/pests/neem-oil-uses.htm It could be a fungal issue, especially if the soil around your plants is too wet. Check the drainage and see if the soil (about an inch or so down) is too moist. If so, allow the soil to dry out some. Neem oil can help with this issue as well. Finally, some types of callas naturally have white-spotted leaves, such as Z. rehmannii.

Yes, you can go ahead and do this now before they get any larger. Just replant them in a suitable location and care as usual.

You can either keep the plant in its pot and continue to grow it as a container plant (indoors or out), or you can plant it outdoors. They do enjoy sun; however, keep in mind that in your area it may get fairly hot, so just make sure that you keep the plant well watered whether in a container or not. Here is an article that you may find helpful: https://www.gardeningknowhow.com/ornamental/bulbs/calla-lily/growing-calla-lilies-and-care-of-calla-lilies.htm If you want the calla to rebloom, this article should help you with that: https://www.gardeningknowhow.com/ornamental/bulbs/calla-lily/make-calla-lily-bloom.htm