Yesterday the download speed plummeted Previously I averaged between 2000 and 3000, now i barely get 700. I can't figure out what I changed. I've tried going through the optimization tutorial but nothing helps. Advise gladly accepted.

individual torrents never exceed 10k now. I wonder if the last update caused this

Mine is working pretty good; full bandwidth of my fiber connection: 2160kB/s or 17200kbps.
Might be traffic shaping, or bad router configuration, or low seeders amount, old torrent, or new but full of peers torrent, other problems, a bad network cable, etc.; the Tixati defaults can handle easily an 40mB/s connection if the hard disk can handle, if fragmented, the random writes.
I do sometimes transfer local by torrent, and they do get 40mB/s.

There is nothing you can do about the torrent side, but yes if its a problem in your side.
Tixati is the fastest GUI client existing, and it do miracles into my seeds.
You can test with the NON-GUI client. If they work full, then indeed the problem is not in the torrent side.