My level seven bard used to be able to cast four cantrips, I believe, but now she can only cast three.

I wasn't sure if this was a bug, a change in the rules, or if I'm hallucinating, so feel free to move it to the appropriate forum.

Check your charisma score and/or other factors contributing to the number of spells that you get? I'm not an expert on bards, so maybe another DM can chime in and mention what those factors are.