Yes, for Germany, our understanding is also that the only senior discounts are on buying a Bahn Card 50 (pay about €128 instead of €255), which gives you 50% ticket discounts for a year: http://www.bahn.com/i/view/GBR/en/prices/germany/bahncard.shtml.
Advance-purchase ticket discounts or a German Rail Pass (with two-traveler discount) are the usual choices for most short-term visitors: http://www.ricksteves.com/travel-tips/transportation/trains/germany-rail-passes.
Senior deals by country that we've been able to confirm are typically listed at the bottom of each single-country page in the rail travel section of our web site (for Austria, Belgium, Great Britain, Finland, France, Germany, Italy, Norway, and Spain). Each one is different.