If you need to shape the plants, you can do that any time now and whenever necessary, really, as long as you're only removing small amounts. Feed from mid April onwards with either Miracle Gro general purpose (follow instructions on pack) or scrape off the top surface of compost, sprinkle some Growmore on and top off with fresh compost, which will keep them fed for the next six weeks. Note that, after two years, its possible they may need repotting.