Upstairs sink is draining EXTREMELY slow, but every other drain in the house is fine.

Hello! For the past month or so, our upstairs bathroom sink has been draining rather slowly. We are used to having to snake the drain frequently, so at first we didn't realize it was a bigger issue, but now it's not getting better.

We snaked the drain multiple times, removed the P trap and snaked through the open P trap to get further into the pipes, and (before knowing it caused more harm than good) used Draino and Green Gobbler clog removing solution.

The upstairs tub has no issues and every other sink in the house has no issues whatsoever. What should be our next step in trying to fix this???