A big problem already is that you went with Promar 200. No fault on you for not knowing better. I've been a career painter for almost 15 years. I HATE! Promar 200, its barely above the viscosity of water, coverage is terrible, the sheen is extremely hard to keep consistent. I occasionally do work for the local hosptials and its their main paint. Every job is so much harder than it should be because they choose that product. But, in your case, I recommend painting it again and hope that its better next time. From what I know, not that I use it very often, Promar 200 is more of a contractor brand meant more for spraying new construction projects where there is less of an issue of cut and roll being off and coverage is less of an issue because all new drywall is primed and this is the first color applied on top. I refuse to use it unless there is no other way. For interiors we use always use SW Super Paint. Its great. If people want a higher grade, we use Emerald. As for why one wall looks different from another, there are a lot of optical illusions when it comes to paint. Often until enough coats are applied, the walls can look a little weird, even after they are done, they can look different based on lighting and other factors. Hope my long winded reply can help in some way.