Here is the link for all the discounts for trains of PKP InterCity company (TLK, EIC, Ex trains) -
https://bilet.intercity.pl/irez/jsp/pokazTabelaZnizek.jsp?info=1&checkJS=true As far as we see, there are special 50% discount for seniors (>60), but you need to have special card (Legitymacja Seniora), which you need to purchase for 75 PLN, valid for one year.
Full list of all the special offers/discounted tickets for domestic connections can be found here -
http://www.intercity.pl/index.php?page=Oferta_krajowa , many of them are as well listed on our Poland page (
http://europetrainsguide.com/Countries/Poland/Poland-PKP.html).
Same Legitymacja Seniora needed for PKP Regionalne trains (OSO, Regio, InterRegio), offers for PKP Regionalnecan be found here -
http://www.przewozyregionalne.pl/aktualne-oferty.html Since not all the info is in English, then we advise you to use google translator, so you can figure out offers you might be interested in. And if you will have any further questions about those specific offers we are ready to help.