Sps unknown pest , please help

[Darakuja]

Since 2 months 3 of my colonies lost color and PE , and looks like some sort of pests eating tissue, I can’t see and red bugs on acroporas or any flatworms or eggs , the only think I can see is some bugs on the bottom of red montipira which is growing very very slow

 

[PeterC99]

Look like black bugs on the red monti.

I used Interceptor to get rid of them. One drawback is that this treatment will kill most inverts in the aquarium.