Just sharing with the community that current Flash 30 has a known performance degradation issue that affects download throughput in Speedtest site.
Details are found in adobe forum - https://forums.adobe.com/thread/2499947
To downgrade flash, can follow instructions below.
PS. AFAIK Chrome does not allow manual downgrade of Flash.
Follow the steps below:
If the Flash installed in the browser is version 30, uninstall it:
Download the Flsh player version 29: https://fpdownload.macromedia.com/pub/flashplayer/installers/archive/fp_184.108.40.206_archive.zip
Disclaimer: Your mileage may vary, i foresee this helps more for people who suddenly encounter low download in speedtest recently.
downgraded to V29 NPAPI,. still get very low download speed.