Perhaps something along these lines, in the "other" option, or whatever you have available in your particular Adoption Agreement. Tailored, of course, to your specific situation. And just for safety, I'd have similar language in the Resolution adopting the amendment.
Effective (date), the normal service and entry date requirements are waived for (name(s)) ONLY, for all contribution types. This special retroactive amendment is for correction under Revenue Procedure 2018-52.