I'm guessing it is because the less expensive locations within the resort, such as standard views or non-preferred location, are no longer available. The actual rack rates for onsite rooms has not changed.
As the others have said, once the rates come out, they don't change. It could be that the room type you were originally looking at is no longer available so you are seeing more expensive room categories that have availability for your dates.
Disney typically raises room prices 1 time a year usually effective Jan. 1. When pricing rooms it's easy to accidentally change something maybe changing your dates will add a more expensive weekend night. Maybe going a week later will put you into a more popular and thus more expensive season, maybe one time you priced it w/ fewer park days on your tickets. But I agree w/ others it sounds like you jumped a view category.
BTW, I assume what you are seeing is for rack rate because it's a bit early for fall discounts, but follow the discount threads here on DIS and when discounts come out grab what you want. Depending on where you stay discounts can range from 20-35% off the room's rack rate, which @ Disney's prices can really help the vacation budget. I would expect fall discounts to be out sometime this summer.
You can add the discount if they have it available for your resort, but the LM rooms have been blacked out of nearly every discount since they opened. You will likely be paying rack rate for those 2 rooms.