Is it worth deadheading Veronicastrum now, not sure if likely to see another late bloom?
I feel that it is always best to dead head if you have the time.
Our best plants for this are the Astrantias and the different hardy geraniums we have. We also dead head Salvia turkestanica. The bees are very appreciative of this as again new flower spikes come for them to feed on for longer.They give fabulous second flush every time.
I don't grow Veronicastrum but probably worth a try.