That shows how little I really know about specific loaches:lipssealedsmilie: Thanks for stepping in Lup.Correct. I keep yoyos and clowns together and have not lost a single one.
It's ironic when yoyos are really something recommended for beginners considering they are very easy to keep and are not at the very least fussy with water conditions.
I'd search everything thoroughly for signs of life. Another ironic thing is yoyos really are not nocturnal fish. Even when kept singly, they have the tendency to show up quite often compared to other species.
I would still test the tank as a precaution, no need to lose other fish. Hopefully just bad luck and bad timing with the new additions.