Extremely slow internet speeds

I recently upgraded my modem to improve performance. Speeds initially were around 70-80. In the last few days speeds have dropped enormously.  Currently they are 6.24 dn, 12.49 up.  Ping test shows no issues.  I have reset the modem and the router.  I am getting slightly better results on my wired connection, but still much slower than it should be for Premier. 50.04 and 6.51 up. 

Speeds have been fluctuating quite a bit.   Can you tell me what may be the problem?  Thanks