Trying to give you a quick answer:
Ideally, it should be from the development branch.
Reason:
Imagine an issue is found for your PR for issue #1, and you need to fix it before merging. If you open a Branch for issue #2 from the issue #1 branch, both of your issues will be blocked until you solve whatever problem was found on Issue #1.
But if you open the branch for issue #2 from the development branch, this means your issue #2 branch is completely independent of issue #1. So you can create another PR for issue #2 while you work on the fix for the problem found in Issue #1.
That was the simple answer.
Now giving you a more elaborated answer, you said you were assigned those issues. From that, I understand you are part of a project, that has a team and it's not just you.
Considering it is probably in a work scenario, I believe the best thing for you to do is to check what is the Branch and SCM policy. Any well-maintained project should have a document with those clearly defined.
If there is no such document, I would check with the other members of the project how they handle this situation, they probably have a pattern that is being followed and just not documented.
In my career in software development, in most of the projects I worked on, my simple answer would apply. But branch rules can be quite different in some projects, and I recommend you check what is the project rules for SCM, to make sure you are following them.