Phone will have 50%+ battery and within a minute of flying it drains to 0.  I have a Samsung Note 4 and have flown many times with less battery than that but last few flights same thing keeps happening.

I'm thinking another app is conflicting with the dji app, but how I would identify which one it is I have no idea.

Any thoughts?

go into your "settings/app" and force close everything you don't need.  How old is the Note 4?  Maybe battery getting ready to bite the dust?