We provide a 0.25% rate bump on CD's for our customers in a specific product. We are going to take away this benefit, which does have a negative impact, but does this require a 30-day advance notice under Reg DD?

How and where was this originally disclosed? This sounds like more of a contractual issue rather than a DD issue. You need to look at your depositor's agreement for how you go about changing the terms and conditions of the account.