Looks like thos acans are slowly dying and receding from the edges.... What you are seeing is the skeleton being exposed and algae growing on it now.
As far as your paramaters hard to exactly pin point what is going on but I would never run my Alk at 10.7...... I keep mine @ 8.0-8.5 and my LPS all do great and grow nicely.
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Justin
Current Tank Info: 25G cube (finally back in the hobby in a small way)
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