2.4 ghz slow speed test

Both 2.4 ghz and 5 ghz used to run the speed test from xfinity or others at close to gigabit speed for downloads.   Now 2.4 ghz is 49mb download and 5 ghz is 300mb download.    I have restarted the modem.    No change.

Should I get a replacement modem?    I have Model: TG4482A