Spin off plan with EACA mandate and changing date of first increase

Looking for guidance. We have a spin off plan effective 4/1/26 with the EACA mandate. The prior RK drafted the EACA to use the first day of the following Plan Year as the date of the first increase. New RK can only use the initial period - 2nd plan year. My question is how to administer for the employees auto enrolled in 2026. Can the new intial period be applied for any of the 2026 auto enrolled participants? 4/1, or could it be retro to employees hired on or after 1/1/26 as long as they get an upddated advanced notice letting them know the first increase will not occur until 1/1/28? I know the conservative approach is to apply the change 1/1/27 in the plan document. Thanks for your help!