The Rhein valley railway is currently closed (actually collapsed into a large hole). There are no trains running in the section north of Baden-Baden to Rastatt. Buses are covering the gap. No ICE trains seem to be going south of Frankfurt. Between Basel and Baden Baden fast trains seem to be running to plan although ICE are replaced by older types. Replacement trains are covering Rastatt- Frankfurt. Because of the need to change twice and use the bus journeys may take up to 2 hours longer.
DB say this situation will continue for "one to two weeks" but won't commit to anyting more specific.
Anyone with plans to travel on this route during August should recheck schedules at https://www.bahn.com/en/view/index.shtml and do so again as you get closer to travel date.