Try not to over complicate it just do smaller but more often water changes with switching to IO. It’s cheaper, has all of the same stuffs in it, maybe just a tad less. Just monitor the big 3 during transition keep them on track and you will be fine. If you dose regularly and see a number creeping down a tad fast then just dose more of that to try to keep it in line. I don’t think trace element is anything to worry about until things are so overgrown.