It seems probable that they were. Joshua 5:5 says the Israelites were already circumcised at the time they came out of Egypt, but their is no record of a mass circumcision just prior to their exodus, which would seem to suggest that the Israelites continued to carry out circumcision during their time in Egypt.
Joshua 5:2 says the Israelites were to be circumcised ‘a second time’ (or ‘again’). This means the Israelites had been circumcised before and then their was a lapse in the rite — but it doesn’t specify when the “first” circumcision was.
It could imply an otherwise unrecorded “mass circumcision” that happened just before the Jews left Egypt; or it could refer to the need for a mass circumcision in Joshua’s day because, although the Jews were circumcised during their time in Egypt, they were no longer a circumcised people: the people needed to become a circumcised people once again.
The second of these two options seems best because of the stress in Joshua 5 on the Jewish children not being circumcised in the wilderness: it seems this is the first lapse in circumcision in Israel’s history and Joshua needs to restore the people to Israel to the position of being a circumcised people again.