HPW is your protein source for you diet, so they need veggies and fruits to eat with the HPW. The same goes for BML. I don't recommend changing to BML if they already like HPW, you would only be swapping one protein for another.
If they aren't eating the fruits and veggies then you need to try putting the fruits and veggies in the cage only. And if they eat them then put the HPW in. They need to be taught that they have to eat all of their foods, not just one. Constantly swapping them out doesn't teach them that. It's just like a child, you can't cater to them. They learn to be picky because they know you will change what is in their cage because they don't want to eat it.
They will eat when they are hungry, they won't starve.