My qtc is always around 405-415ms as a 30 year old male shouldnt it be always under 400 and in the 300s?

no. Your corrected QT is normal if it is less that 440 for sure. It can vary through the day and evening

The QT interval varies with the heart rate, generally being under 400-440 milliseconds in the male. It is important to know that measurement of the QT interval can be difficult since the end of the T wave is not always distinct . You have not mentioned the heart rate; it is important to have that information. I would reassure you but if it is worrisome, please have your doctor look at the ECG.