One couple drinking milk, the other not

[dakillakm Resident]

Since Navana seems to have her situation undercontrol, I'll steal the thread to ask you guys another love questions. I had two cats who made a box last week. Both were in the same area all week, both drinking milk (presumably), and yet they somehow got 4% off from each other. Now, during this time a friend did an accidental parcel return and they ended up in my invy for maybe half a day. Could this have effected it or what do you think threw them off?