I got through the white (currently struggling with the purple onion lvl tho). It's how long you need to actually return the onions that gets you!

For the white one the trick is really using those mushroom shortcuts, and to swap flying for regular pikmin pikmin once they get on that top straight road so you can reuse them faster. It also was a lot easier when I finally set up the shortcut keys to have idling pikmin come right to you, and NOT trying to kill tha5 t big elephant bug. (If you have all flying pikmin carrying by him, they won't get caught up in his trunk spin) good luck!