Wow, I love this! That middle tree, especially, is looking great. Some stuff that stood out to me:
-savannah trees often have redder bark, like in the reference. I'd also strengthen the hue shift on the trunks.
-try yellower, less saturated foliage
-baobob trees come in many shapes, but ones like your ref are a lot taller and thinner. baobob trees also tend to be much taller than acacia trees (your middle tree?).
-the point of origin on the centermost branch of the baobob is a little weird. It's hard to tell if it's coming from the front, back, or center.
-the way the foliage is lined up on the baobob (all in a straight line of leaf tufts with the edges barely touching) makes it look like the canopy is all on one plane instead of projecting radially. Maybe darken some of the leaf tufts to make them look like they're behind the rest/add a couple in front of the branches, like you have on the center tree?
-the cluster of pockmarks along the bottom of the tree is a little visually distracting. thin them out, maybe?
-it looks like you copy/pasted leaf clusters into a rough canopy shape for all of these. it looks pretty good, but savannah trees (including acacia) tend to have flatter canopies, not so much tufts of foliage arranged into a sphere. I don't think you need to completely redo the leaves or anything, but maybe reshape the silhouette a little?
Edit: Color suggestion