Seems that my addition of compost was a wake up call for the Columbus plant at least. Here's what I found just a couple of days after applying it:
And then a couple of days after that:
Still no signs of life from the other two plants. Seems winter means that we'll be starting a little later this year. I'm going to be away for 10 days so it will be interesting to see how much the Columbus grows in that time and whether the other two decide to grace us with their presence.