Is there any way to make multiple objects convex hulls? Is there a way to make multiple objects become convex hulls using python and applying the operator to all selected objects?
Use the bmesh operator
Use the bmesh convex hull operator as outlined here https://blender.stackexchange.com/a/121815/15543
Test script, run in object mode. Turns all selected mesh objects into their convex hull.
import bpy
import bmesh

context = bpy.context

meshes = set(o.data for o in context.selected_objects if o.type == 'MESH')

bm = bmesh.new()
for me in meshes:
    bm.from_mesh(me)
    bmesh.ops.convex_hull(bm, input=bm.verts)
    bm.to_mesh(me)
    me.update()
    bm.clear()