Publication from PhD thesis
What a journal will publish is up to them. So, whether is is a problem is up to the editor(s). There is an advantage to readers if the two articles are in the same journal, but also if you just publish a single long article. I doubt that it matters much for your reputation whether the two articles are in the same or different journals. Having two papers instead of one is good, but having a longer, highly significant, single paper is also good. 

But, let me point out that you may be building in a problem for yourself with two papers. It is possible (likely?) that the novelty and impact of each of the two papers is lower than that of a single paper. If that is the case, then you lessen the likelihood of either getting published. But you know the material and you may be fine here. 

I would proceed strategically, however. First outline the two articles and get a good sense that both would pass the threshold of publish-ability. Your advisor can give good advice here. Then, develop one of the papers completely (rather than both) and get it off to the most appropriate journal. While that paper is in progress with the journal, develop the second paper. Make a decision about whether and where to send it based on what you hear about the first paper. 

This gets you into the process earlier than if you spend the time to complete both papers and also gives you feedback. 

In the worst case that the first paper is rejected or requires a lot of revision, you can then submit the other to the same or another journal, or, potentially, make a further strategic decision about how to proceed. 

This seems, to me, to be a better option than spending time to develop both to the same level and sending them both together. But that is only an opinion.