Ashkenazim have different נוסחאות for selichos:
- Minhag Lita
- Minhag Polin
- Minhag Medinas Ashkenaz
Each Shul has the nussach it follows.
If an individual is davening סליחות in a place which is saying a nussach which is NOT the one he usually uses, he must still join in and say the nussach of the tzibbur with which he is davening. If he davens in his regular tzibbur the next day and finds that they are saying one or two selichos which are a repetition of what he said the previous day, he must still say them again with this tzibbur.