If you have been using Lauke pullet Grower it is a good quality product and is medicated. The Lauke Red Hen range is not medicated. The medication in the feeds works by keeping the coccidia at a low level whilst the chicks develop a natural resistance. They will succumb to Coccidiosis if they get a massive challenge (eg damp conditions) before they develop sufficient natural resistance - that is the time for additional medication - either preventative or as a treatment.
By the time your hens are laying Coccidiosis should not be a problem so it is unlikely to need to treat them.
Baycox is generally considered as the most effective. You can buy smaller quantities of it herehttp://www.geckodan.com/product/toltraz ... cidiocide/
Danny also has is also another single dose product - Diclazuril but I know nothing about it. Hopefully some one else can provide some information.