This is a good cause for a filing a case in High Courts. The CIC and SICs have been ignoring the plain language of the RTI. There are numerous cases where CIC, and SIC found that the information was not released in the stipulated time, yet they did not impose the mandatory penalty.
I do not see how filing a RTI application with CIC, asking for reason why penalty was not imposed, is going to help. RTI allows you to get documents already in existence. There are no documents that will tell us why they did not impose the penalty.
If the idea of filing RTI with CIC is to make them aware of the problem, then it may be a worthwhile task. In any case, filing RTI application is such a simple process, it is good to do it, before undertaking a complex task of filing a writ in the High Court.