Q.Can a hanging basket of lobelia become root bound?
It looks like the greenery is dying, I’ve been keeping it well watered and it gets both sun and shade. I’m wondering if I should transplant into a larger container.
Thanks for any help!

Certified GKH Gardening Expert
While it isn't common, it could be. There are quite a few reasons that this could be the case, though. It is best to look at it from all possible perspectives.
This article will help you to narrow down the possibilities that it could be: https://www.gardeningknowhow.com/ornamental/flowers/lobelia/lobelia-plants-turn-brown.htm