As I see it you have two questions.

The legal one should be easy. My state, for example,doesnt allow baiting and they define baiting ashunting over the bait or taking advantage ofany pattern that could be construed as being affected by the bait and extends to 30 days after all bait is gone even if you don't know the bait is or was there. Check your local laws first. Also consider that many folks feed through the winter and the feeder may be empty well before hunting season in which case you're OK anyway with the legal issue.

Laws are easy, they're usually a yes or no or black and white issue. Morally, what's right is a little tougher. You didnt put out the corn and salt but now you know about it. You had already found the sheds and were already scouting the area. So far you're on the moral high ground. You have to survey the situation and askyourself honestly if you're taking an unfair advantage. Only you know the true answer and the fact that you're asking for advice on the issue means that you want to do and likely will do the right thing. Continue watching and learning and hopefully, the bait goes away in the summer and you have no issue. If not, pay attention to the lay of the land and the obstacles in the area andask yourself if the trail you're watching is there because purely of the bait or would it have been there anyway.

good luck! I hope your discovery of the feeder doesnt ruin your chance at finding a nice set of horns while they're still attached to the deer!