I’m concerned. I’m 53 y.o. w female. I’ve been on generic Ritalin- methylphenidate 20mg 1 and 1/2 tabs 4x q day. It works well for me. Today my refill has been switched from Corapharma to KVK-TECH. I’m experiencing strong headaches. Never had this before. I need never heard of KVK-TECH??? Anyone else?