26qb - penalty notice received

I have purchased an under construction property for which I failed to deduct TDS while making payments to builders. However in Jan 2016, I made the payment of TDS to govt along with interest @ 1.5% I now have received a demand notice for penalty due to late filing of 26 QB. My questions are 1. I have filled and submitted eight such 26QBs (one for each installment payment) Any idea why have I got the notice for only one such 26QB and what are the chances of getting the notice for others? 2. Possible options of responding to this notice?