Most of my birds nests have white tips with white polyps when they are happy and growing. Other SPS don't always grow like that though, My acropora nana never get white tips unless it is super ****ed off, or ive done something wrong. The white tips on that coral never live, usually get algae on them.
Just keep an eye on them, if they start to get algae, or go brown then its to much light. Another way to check is to take a photo of the corals and then keep taking them in the same spot a few times a week. Then you can see if it is growth or bleaching.
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