DIY Rocks cape, cement flaking off.

[CobrahSparkles]

When setting up my tank I had 3 HUGE rocks I wanted to use as the only rock in the tank. They do stand up on their own but obviously I was preparing for the worst. What I did was use hydraulic cement to make a sort of upside down T shape with the rocks to give them a larger base area. Tank is about 5 or 6 months old now and I'm noticing pieces of the cement I used flaking off onto the sandbed. Is this something I should be worried about? Is it just the excess cement that's not actually holding the piece together? The base area is covered by crushed coral so I can't see if it's still attached, but based off the small amount of concrete I've seen I can only assume it still is. Thoughts?

Here's a pic of it to hopefully help you understand better.