Thanks Mike for your perspective.
These forsythia are part of a privacy hedge, so drastic cutback is not
an option.

However, if I were to just prune now, by mid Aug there would be 6 foot
high spikes ...every year I have pruned the same way and typically have
full flowering except these last two seasons.

I am tempted to trim now and not touch it again just to see what
happens ...but I think it is environmental, since I have not seen any
decent displays anywhere in our area

Stew Corman