I suggest you cross-pollinate them, now‘s a good chance to get some more 
I will try to do it, hopefully today the second flower will open more, and there are two more coming up,

It is too cold still to any insects to fly so there is no chance of them doing the pollinating.
Thanks for the suggestion where it grows best. There is not much online about it, and I have Janis Ruksans book of Crocuses but it is the first edition and there is nothing yet about C.gramensis.
I think I will plant them in semishade where Crocus thirkeanus and Crocus olivieri do well, in a bed under an apple tree.