Perceptol and Microdol-X are based on D-23, purportedly with slightly less Metol, and the addition of Sodium Chloride. Microdol-X included an anti-silvering/plating agent.

RLS is a MQ developer, which is not the same thing. Further, there is nothing inherently abnormal about the keeping properties of D-23 type developers once mixed, not are they prone to any kind of inherent "sudden death".

RLS is a different formula and is packaged as a liquid. A one-part liquid developer requires careful formulation and packaging if it is to have a long shelf life.