So, I went to R1 went there was a swarm of Farfecth'd. 2 Farfecth'd were Lv.54 and Lv.51.
Do you mean Route 1? If so, no, it's not a glitch, if it was part of a swarm. Those Farfetch'd could have been any level from 15 to 55, so the level is not a glitch, and nor is the Pokemon.
You were probably walking tall dark-green grass, where there is a chance to get a double battle. No glitch, don't worry. The Pokemon are meant to be this high-levelled.