Those are replies to your subscriptions - threads that you follow. If you didn't choose to follow them, check your settings. It might be set to subscribe to any thread you have posted in in the past.
You may have accidentally hit a button that causes you to follow some stuff you didn't intend to follow, it happens to me every now and then on my phone.
Click on those topics and look at the top on the right side and it will show a button where you can unsubscribe.
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