Thanks for the comments, everyone.
When I signed up for this in December, I thought I'd be putting quite a lot of effort in every week; coming up with an idea that worked and then translating that into a photograph. Somewhere along the line I realised I needed to spend time on my normal photography too, otherwise I'd soon lose the will to live... Since then, some weeks I've just not been feeling it at all, and instead of falling behind even further I've resigned myself to stretching the themes slightly, to make it easier to come up with something, anything, that will (sorta) meet the requirements.
Although I do love photographing flowers, Random is certainly NOT one of my best... Another candidate for whenever the first Reshoot is drawn!