A common symptom of overwatering is a browning of the leaves. To ensure that your plants are receiving an appropriate amount of water, check that the soil is dry by putting your finger deep down into it. The soil should be dry all the way through, not just on the surface. Most people water their houseplants a little bit at a time. Once your soil has dried completely, place your plant in the sink and run water over it, allowing the excess to drain off.
Viruses are another common problem with houseplants.
They cause a slow and general debilitation of the plant. In fact, viruses behave in plants much as they do in people. Unfortunately, a plant virus usually signals the end for the plant it has infected. It's very important to move infected plants away from healthy plants so that the virus doesn't spread. I can tell you that mini-roses aren't really built to survive indoors.