It is not uncommon when using birth control pills like Marvelon to occasionally have spotting. Most likely, that is the reason for the spotting. I am not aware of any connection between lemon juice and spotting, so I doubt that it is related. Usually, it will resolve on it's own while you continue the pills. if it becomes a persistent problem, you can talk to your doctor about switching to a different pill, or to a higher dosage. I hope this helps, please let me know if you have any more questions.