Don't worry, you should give more time to referees. Some of them are very busy. I usually provide them a two-week or longer deadline saying by when I want to mail out my application. You can send out a friendly reminder email after the deadline if you haven't received the letter. But frankly, 5,6 days only, you have nothing to complain :)
适当催促一下,比方 I truly thank you for writing the letter for me considering your other obligations. Please let me know if you need anything else from me before you send the letter. etc.