I added a healthy dose of stability after a 25% water changeIf along with the 4 platies, you purchased at least 8 plants that immediately take, you may then be able to short citcuit the time it takes to grow a large population of beneficial bacteria, enough of a population to process toxix=c ammonia, because they will be among those plants.
Cycling is the process of building a large enough bacterial population to consume all the ammonia produced by the fish.
Random question but I saw one of my platys chasing a female relentlessly and rubbing against her. Did I just witness them mating in a cycling tank lol