|Perhaps Chocolate Tube slime mould, Stremonitis splendens.|
Checking on the internet, it could be a Stemonitis sp. perhaps the Chocolate Tube slime mould, Stemonitis splendens. It states that the white and pink form is very short lived and soon turns brown, hence the name!
Stemonitis is a destinctive genus of slime moulds found throughout the world (except Antartica). They are characterised by sporangia supported on slender stalks, which grow in clusters on rotting wood.
Any slime mould experts out there?