So offering qada salah is bidah now? While it may be performed at the mosque, all qada salah are offered individually and not in jama'a
No, but if you believe offering a certain prayer (Qadha Salaah) at a specific time (3 days of Laylatul Qadr) when the Prophet (saw) didn't prescribe it, is considered a bidah. At the imambaras here where I grew up and from my relatives in Afghanistan, we all do it too. It consists of the local mullah leading 6 days worth of Qadha Salaah in jamaat for each of the 3 nights.
I mentioned it, because I've always heard from my relatives and local community 'Why would Allah prescribe a hard Sunnah like Tarawih when we fasted the whole day and our stomachs are full?" and "They (Sunnis) have no evidence for it." When these prayers are clearly harder then Tarawih, physically exhausting, no-one ever second guesses it or asks for 'evidence', and assumes that we or someone who has haqq on us has accumulated over 18 days worth of Qadha in just one year!
If you're seriously worried about having Qadha and getting the full potential of Ramadhan (not just Laylatul Qadr), finish your Qadha before Ramadhan and spend Ramadhan (especially the nights of Qadr) in dhikr and sunnah prayers, not doing an exhausting 'up and down' excercise done in 'jamaat' on the day you should've been doing Sunnah, not making-up Qadha.