Why are the diodes in this circuit forward biased in spite of no current flowing through them?
Isn't it supposed to be "off" since SCR1 is not triggered yet so the there's no current flowing in the path


Even when blocking, the SCR will allow a small leakage current through. For the first type I checked, this current is limited to 1 uA at room temperature or 100 uA at 125 C. 

Even though this current is small, it is enough to develop a forward bias (maybe only a couple 100 mV) across the diode.