Thanks Tindo,
I do try to keep humidity up when I can, I think that when I'm forgetting to water I'm also forgetting to do anything about humidity (regular water on the greenhouse floor helps) so for me the two are linked.
I bet it's high just now, didn't look this morning but it's been raining all night and the door was open so probably high humidity in the greenhouse
I'm not to worried about the growths as while are couple of struggling to free from the sheaths there are lots that appear to be doing fine. At one time when I first got this they were all doing it, so one or two out of so many growths is not so concerning.