explanation????

The bottom FR test and the 88 cent test were both taken last night. Middle test this morning. Just took a FRER digital and it said No. Are the first response digital tests less sensitive than the mechanical ones? I know clear blue digital requires a greater hcg concentrate but didn't know about FR digital and let me tell ya we are confused as hell please help!! Also FYI the lines appeared within 5 minutes and have stayed like that