Chicken feeds are pretty similar, so a sudden switch shouldn’t matter much at all.  We’ve gradually changed feeds before (as described above).  However, we’ve also had the occasion where the young chicken keeper in the house didn’t notify us of low feed and HAD to get some that day, but due to schedules etc could only pick it up at another store than usual -therefore, a different brand but same type (ie “grower”).  No issues noted the times we suddenly switched.  Poops the same, activity the same, etc.   we’ve had to do sudden switches on our chickens (laying pullers and older chicks), and quail and none suffered.  
Btw, because of this we did discover a feed we really like for the birds and became aware how much better they were doing on different feed as compared to the other feed we had been using, so one good point to the chicken keeping kid not being great at keeping track of feed levels.