Question about Youtube commenting bot - all comments get flagged as spam instantly

Hello,
I recently wrote 2 bots for youtube commenting.
They send youtube comments automatically (every (random) minutes).

1st bot is written in PHP and the second in VB.net.
They use web requests (not API).
They both worked fine for about 3 days.

The problem is: all comments I try to send via this bot are getting flagged as spam instantly.

I tried:
-> using fresh, HQ, private and never used proxy
-> using new accounts
-> changing header information (like different browsers etc.)

What's more, when I use normal browser - it works for the proxy and the account I used in my bot, so I'm nearly 100% sure, that the problem is in the code of my bot.

is there anything that might help?
Regards.

Check your http headers. Make sure there are "referers" in your requests. Check your user agents as well. I'm not a youtube master in any way but I have played with it for a while and the best way it seems so far with me is to try and duplicate what ie, chrome and firefox are passing to their servers.

yeah, it's absolutely ok. I use wireshark to compare them to browsers and the requests are identical.

yes, every comment is different. It's not a problem.

when I post a comment using new account and some proxy via normal opera browser - it works.
When I post a comment using the same account and the same proxy via my bot - it's marked as spam.