Hi Nick
Welcome to the forum
My first thought would be have you got the right fly on? I think the majority of time people over emphasise patterns however at this time of year trout can become very selective feeders especially when on or in the surface....eg look out for lots of very small white upwing flies (caenis). When these are out it is largely game over and there have been plenty of threads on the subject.
Try and match the hatch so if you see big daddies use these (no hard and fast rules but tend to be best late season). If it's tiny midge go down to size 20's. In each case match the breaking strain. For daddies and sedge you need a tough leader as you get smash takes...6lb is about right but if they are being choosey try a fine fluorocarbon.
If I was fishing size 20's I would usually use a 3lb fluorocarbon .
Also ALWAYS degrease your leader as it will naturally sit in the surface film distorting and refracting light...fish can spot it easily. Permasink is good as it takes the shine off as well. If I am using dries on a calm day I often use an intermediate braided leader to ensure the leader is sunk.
Ginking is good but don't over do it on calm days. You often want the fly sitting in the surface film rather than on it like a shuttlecock
Tight lines
R