Answer: The most common reasons for flower buds not to open correctly would be a root rot problem, underwatering, or cold temperatures. Root rot usually shows up as yellowing leaves or dark tips on the flowers. Underwatering could also cause the blooms to shrivel -- some types of callas require very wet soil during the growing season while others will tolerate soil with damp to average moisture. Cold temperatures could also cause the flowers to fail. Since the other callas seem to be fine, I would suspect one of the first two problems.
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