I suppose it's feasible that, given the withdrawal of fem7 for re-formulation, other patch manufacturers, particularly Evorel were swamped with demand and somewhere in the supply chain they decided to level this out. The domino effect would continue with other E only patch manufacturers. Don't know enough about supply chains but one large player pulling out would have a huge impact on the others. Can't understand why they weren't more prepared though? We're talking very big pharma here, this can't be a new thing and so I suspect Brexit stockpiling plays a part to some degree.
Hopefully, the initial high demand is now accounted for and some manufacturers have adapted to that demand, thereby evening out the supply overall.