Q.What Is Wrong With My Rainbow Eucalyptus?
I purchased a rainbow Eucalyptus Tree.Transplanted it in a larger container until our rainy season started (Florida) I recently noticed that the lower branches were dying, leaves turning yellow. Contacted the company. They told me there were 3 reasons that would cause this. Two did not qualify. They told me that is may have lacked phosphorus. Put 1% around the tree. Please help.

Certified GKH Gardening Expert
I hope you live on a large property. These trees are capable of uprooting sidewalks and structures.
So, did it go from the nursery pot to a larger container to the ground? It may be suffering some transplant shock. Keep it well watered when rain is lacking. They also need full sun. Another thing you can do is remove the grass around the base and mulch it out to the canopy line. It won't have to compete for nutrients and water with the grass.
Here are more care tips:
https://www.gardeningknowhow.com/ornamental/trees/eucalyptus/rainbow-eucalyptus-tree.htm