Derwent Inktense Pencils

Don't know why but watercolour pan paints always go mouldy on me. I bought myself some Derwent Inktense Pencils that are water soluble to see if they might be a substitute. I did a quick painting of a Tree Peony Flower today and I am reasonably happy with the result although I found it hard to mix enough colour at a time and with watercolour you need to work quickly so some hard edges have occurred and lifting the colour was starting to damage the paper.