The Devils remain in the bottom three of the table and are six points adrift of a top six place needed to reach the end of season play-offs.
They were always on the back foot at Ipswich after trailing 10-2 following the first two heats and managed only four race wins throughout the evening. Jack Holder top scored with nine (paid 11) including a win in his first race.
The Devils again suffered at reserve with two points, both coming from Rafal Konopka, guesting for Roland Benko, while the Ipswich reserves scored 13 points, including eight (paid 10) from former Plymouth rider Ashley Morris.
Ipswich: Danny King 10 (5 rides), Cameron Heeps 5+1 (3), Gino Manzares 7+1 (4), Rohan Tungate 8+2 (4), Nico Covatti 13 (5). Reserves: Stefan Nielsen 5+1 (4), Ashley Morris 8+2 (5).
Plymouth: Ryan Fisher 7+1 (5), Morten Risager 5 (4), Jack Holder 9+2 (5), Todd Kurtz 6 (4), Kyle Newman 6 (4). Reserves: Rafal Konopka 2 (4), Sam Simota 0 (4).