Working in customer service my whole life it’s safe to say that no, you should not. I get that you were totally blindsided and I would feel that way too. However bad business spreads fast by word of mouth - and guaranteed the customer will not take the added charge very well. You might suffer a bad review, bad word of mouth, and most importantly a bad experience for yourself as some people can get defensive and hostile when it comes to money. I would recommend giving your clients a review on how there dog was during their stay in a positive and informative way. The higher level of service you give before asking questions and after explaining their stay, the higher chance to avoid these instances. I personally have a pre-req that the dog must be house trained. If after their stay, they show they are not, explain that to the customer if they try to re-book. Some things are left better untouched. As for your rug, do you have house/ renters insurance? I’ve been able to get some things repaired under mine. Worth looking into. Hope this helps. Happy dog sitting!