Painting over flat paint in bathroom
Ok, I'm sure this has been answered before, but I just want to make sure that I'm doing the right thing...our house is 5 years old and we have been living in it for approx. 4. I decided 2 months ago that I wanted to paint our guest bath. Not knowing ANYTHING about paint other than what color I wanted, I chose a cheap (I know, I know) flat interior paint for the walls--we didn't re-paint the ceiling. The walls were originally painted a flat off-white color--I went for a medium brown--called "Ottertail"--we used 2 coats. Now, 2 months later, the paint is starting to discolor around the shower--blotchy darker areas, and I hate how chalky the flat paint looks. Obviously most of the problem is from the cheap paint and the humidity in the bathroom. From reading other threads on here, I know now that I should've used a paint made specifically for bathrooms and NOT cheap paint. So, what's done is done, but I want to fix it, because I am very disappointed in the result! First off, do I need to re-sand or re-clean the walls before re-painting? Secondly, do I need to use a primer over the flat paint, and if so, what is recommended? Third, what is a durable brand of bathroom paint (I don't plan on re-painting again for a long time if possible)? Fourth, do I need to go with a lighter color (I'd say it's about the color of chocolate milk now), and if so, would I need to prime it to cover the brown? Thank you for any help you can provide!!