Fallout – Why is Kellogg automatically hostile to me

In my experience if you plant something near the bugged plant, assign a settler to that plant, and let the farming run its course, these issues tend to resolve themselves over time.

I've had invasions occur ON my farm plots, and have watched my missile turrets decimate the farm plots, and then not be able to select the destroyed crops.. Poor farm/defense layout aside, this is the circumstance in which I came back later and notice that the plants were eventually revived.

In short, I wouldn't worry so much about micro-managing the efficiency of every single plant. If food and water is sufficient for stability or growth, that's good enough for me!

I had the same issue, but eventually Danse just suddenly started talking about the quest shortly after Brandis was found. Supposedly Captain Kells can also complete the quest, according to the Fallout 4 wiki:

If the player character puts off completing this quest until after Paladin Danse has become a potential companion, they may be unable to turn the quest in as he will only offer companion dialogue options. However, after a period of time the mission turn in point will be transferred to Captain Kells, allowing for completion.

http://fallout.wikia.com/wiki/The_Lost_Patrol