Those little yellow sz 20 flies are most likely little craneflies. I have seen trout rising to them too. I fished at Nances Friday and did really well with a sz 14 pheasant tailed soft hackle flymph (wood duck tail and brown/gray partridge collar). I also did well during a brief afternoon hatch of light yellow colored sulphers using a sz 16 comparardun very similar in color (light yellow dubbed body) with a light tan deerhair wing and light ginger hackle split tails. The water IS warming quite a bit there and even the smallies are up at the tailout of the riffles.