It is day 19 and no sign of pipping so I'm wondering if they start pipping later in the evening or day 20?
Hatching depends on so many variables that I would not worry about it too much. If NONE have pipped so far, just wait. My Silkie eggs "usually" pip on day 21 (if you count egg-set day as day zero), but they can pip as late as day 23. Hopefully, your humidity was not too high during the first 18 days; everything should be fine. Did you candle the eggs just before lockdown? (I edited to add correct dates.)
Yes I candled before lockdown, they seemed to be happy and healthy and no pip today.. well I'll just hope for the best!