The only way you could do what you describe with the Journal plugin would be to have a new Journal activity each day, with it's 'Day's available' set for 1 days. This is due to the way the journal saves each users entry in the database. It is just ONE entry per student that grows in size each time they add to it. There is no way to limit their access to just part of their entry.
Journal (plugin)
journal as a diary
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