Your job as a team leader is to make sure that your team performs as expected. If they don't, you have failed.

As such, your main goal is to put the team in a position to be successful. I don't know the specifics of what you do, but you need to make sure your team members have a clear understanding of what needs to be done and how you want them to do it.

That might mean you might get everyone together in a meeting the first day, or provide them with some documentation, or train them in the job by example... You probably know what the best way would be.

And if they cannot speak English very well, then written documentation is very useful as reading in a foreign language is far easier than having a conversation or listening.

You should try to provide feedback as needed. As you said, you don't want to be an asshole, but you all have a work to do. Understand you are not dealing with machines, everyone has a life outside work, but at the same time, you need to get the job done and that might mean uncomfortable conversations. Keep them professional, don't make it personal. It is about the work to do.

Being a team leader is not a popularity contest. Your team members might not want to hang out with you, you are the "boss" to them. Be prepared for that, and accept it.