They are 4 weeks old now, they can be on fewer milk feeds a day. They will get hungry yes, that will help them start to tinker with the creep!
I would drop one milk feed now, and if they still aren't eating creep at all in a week, cut the bottles to 2 a day.
You can increase the amount of milk per feed so they get the same quantity overall, but do that in small increments so they don't get stomach overflow. You may need to reduce the overall milk ration to get them to eat creep, but the first thing is to give them time to get hungry between bottles.
Does your agri store do an "all stock" mix? Most do. Otherwise get some cereal flakes (maize or barley, or triticale, whatever is available) and maybe some squashed peas. Mix some of that with the creep, it will make it more interesting to them. It's just about teaching them to eat it at this point, you can worry about getting the right nutrients in the right balance once they are eating it! They will eat the pukka lamb creep once they have learned about it.