Corals refusing food

[dodgy67]

I have been trying to feed my corals Mysis shrimp placing it directly over the mouth, but both my Balsto's and Chalice are shrugging the food off, any ides why

 

[Member No. 1]

How often are you trying to feed them?

Once a week is more than enough.

 

[dodgy67]

The Chalice corals are fairly new and have never fed, but the blasto used to feed every time I offered food.