No, if you have used Kilz paint as a primer on your bathroom walls and ceiling, it is generally not necessary to apply an additional layer of primer before painting with your chosen colors. Kilz is a high-quality primer that is specifically designed to provide excellent adhesion and coverage, making it an effective base for painting over. However, it is important to ensure that the Kilz primer has been properly applied and allowed to fully dry before proceeding with your chosen colors. Additionally, if the surface you are painting on has specific issues such as stains, odors, or water damage, using addional coats of Kilz primer or shelac primer for those issues may be necessary before applying the paint. Overall, using Kilz primer before applying your desired paint colors should suffice in most cases, providing a durable and long-lasting finish for your bathroom walls and ceiling.