Prior to that, the Rams had won three and drawn one in four Championship matches - a run that included a 3-0 thumping of league leaders Newcastle.
Tonge told the Derby Telegraph: "We went on a good run but then felt a bit aggrieved to lose to Swansea and it was a similar feeling after the West Brom game.
"At least we're playing quite well. That is a definite plus and we've just got to keep that going.
"I'm sure if we can just cut out the few mistakes we are making, we will be fine. If we weren't playing well, I would be more worried."