Got it - thanks Aunt sally
You must have had a tidy up while I was gone!
I just tried a few nasturtium leaves (minus the stems) on the girls and they fought over them!
I will leave it at that for tonight (three leaves each if they share nicely) and see what reaction I get tomorrow if I offer them some more.
Just getting short of free greens from the garden about now and the Swiss chard and perpetual spinach isn't big enough to pick yet.