Add an indicator within the group and set it's expression to use SWITCH to return a suitable value to show the relevant indicator

Use IIF to test the field for yes and return 1 or zero, put this in a SUM

Add SUM to the SWITCH and test the value of SUM to be > zero to return a value for the required indicator

Repeat this for no and null

e.g.

=SWITCH(SUM(IIF(Fields!Passed.Value='yes',1,0))>0,1,SUM(IIF(Fields!Passed.Value='no',1,0))>0,2,True,3)

(Set the indicators test ranges to 1,2 and 3 accordingly)