for fall feeding usually 2 parts sugar/1 part water. If they are still bringing in nectar they may ignore the sugar water

Exactly. They probably don't need it. There is likely a flow going on and they are collecting their own nectar.

not sure what "trays" you are using... or if it is too much water, my guess is, in August there are plenty of wildflowers and they don't need it.

I can share what I do...for winter: cook the 2 parts sugar to 1 part water until all is dissolved, let it cool, put in ziplock/hefty style baggies, put in a dish/tray on top of the inner cover, inside an empty super...(cut a few slits in the top of the baggie), then put the hive lid on.

I'm in Oklahoma and we have crazy days where it is 60-70 degrees in January and February and the bees love to come out... so in the fall when I have too much fruit, I make "hard ball stage" candy-syrup from sugar and juiced pears. Then when we have these weird warm days I put the syrupy candy out on specific designated rocks in the orchard for the bees to enjoy. It encourages more cleansing flights.