The answer may depend on the country and the industry you are working in.
I am working in the IT industry in the US.
While I have nothing against "sending thank-you notes after the interviews" as it may be a good way to widen your contacts and networking, I have always chosen not to do that.
I usually thank the interviewers directly at the end of the interview. To me that is nice, professional, and diplomatic enough. I believe there is no need to send "thank-you" notes after the interview as it may be redundant.
Plus, the interviewers may be too busy and don't have time to read these "thank-you" notes. Some of them may find it unpleasant that you send them extra notes and communications while they are busy. Overall, most interviewers simply prefer that you patiently wait for their official decision on whether they would hire you.
(Now, if you have not heard from the interviewers 3 weeks after the interview, then you can send them an email asking them about their decision if you want to. But, that is a different topic).
Note: Again, however, other countries and industries may have different preferences about sending "thank-you" notes after the interview.
If possible, would you please mention the country and industry you are in ?