Unknown polyp or mushroom on new rock

[saltwaternewbie12]

I found 2 of these on a new piece of live rock I added. The rock also has 9 or more Kenya type trees on it too..... The thing in ? Is the round thing just below the little brown tree coral.... There is also a dark purple one too but it can't be seen in the pic. Any ideas what it may be?? Sometimes it appears to have a clear type "trunk" that I can see.