In a marital relationship there can be many reasons for differences.
There may be many things where you need to know what exactly is wrong and what exactly is wanted.
Like there may be difference of opinion or there may be mis understanding or communication gap or many other reasons.
But as you know they want peace and harmony then
1. Request VK for peace and harmony in the relationship.
2. One Soul Serum to the couple.
3. If anyone is a VK users out of the two then use Love Serum.
4. Read https://www.litairian.com/switch-words-increase-spouses-love-intense/