Good idea to warn students they were suspected of cheating?
No, you should not single them out. If you have evidence of cheating, then charge it. If you have suspicions then you should swallow and ignore them so as not to prejudice the students in the future.
If you want to announce to the entire class that there were a few other cases that were suspect, not naming names and not singling out any individual, that would be fine and the message would be delivered.
Some people would take such a singling out very badly. Psychologically. Especially if they didn't cheat.