Stocked bows

Hi,

I am still a newbie when it comes to flyfishing but not fishing in
general. Recently I joined the Dallas Flyfishers. I can't say enough
nice things about this group! Very helpful members and had a great trip
to Broken Bow, OK last month with them.

Texas stocks our local ponds with rainbows over the winter but the water
is too warm come spring so it is catch and keep for most people fishing
for them.
I have tried numerous flies trying to catch them with zero success.
All the while the guys fishing right next to me with spinning rods and
bread dough balls or power bait are catching one after another.
The trout have been fed pellets or so I have been told.

Any particular fly pattern that would work with these stockers?
I tried caddis flies that are brown like the pellets in their wet,
exploded form but that didn't work either. Nymphs, midges, pan fish
flies...etc nada....

Thanks,
Don
Allen, TX