Terrible Upload Speed

I noticed a change in my upload speed in early May.  I have 1.3G service and was getting 600Mbs speed for the download (which is great), and today have 1.6Mbs upload speed (which is terrible).  Earlier this year it was 30Mbs upload (acceptable).  The upload speed results in occasional large files taking several hours to transfer.

The question is what changed and why is Xfinity throttling the upload speed so dramatically and how can I fix it?