To me their worst music period was towards the end of 2010 when they released Løve Rainbow , Dear Snow & Hatenai Sora which were all really boring (ok the PV for Hatenai Sora saved things to a certain extent)
And their worst PV was Dear Snow which was a big major bore
When they released truth , it was amazing as they never had a dark angsty song prior to that release and Breathless was a great follow up to the dark route (and Platinum Data was pretty good which I watched it when it was shown here in cinemas)
Their last 2 singles prior to I seek / Daylight all centred on love lol