Severums love to eat plants and JD's (thought I saw one in your photo) love to dig.
Your best bet plant wise is Amazon Swords, java fern and anubias. The severum does not like the taste of these.
Get large specimens if you can as they will handle a slight beating until they get established.
FYI ambulia is a stem plant and far too fragile for your cichlids.
Good luck!