Hello I bought an Acer (Japanese maple) last from the garden center which had two lead branches that weren't connected above the soil line.

This year the leaves have started to form and the plant is really growing well on one of the two leaders (as you can see from the pictures) however the second leader the leaves have shrivelled and are dying.

What should I do to maximize growth from the plant?
Do I remove the recessive "upright" to allow the dominant to grow?
If so, when should I do this? Now during growing season or wait till late summer

Thanks!