I'm no expert but .....The other day when Matilda was laying an egg I noticed a couple drops of blood dripping from the nesting box before the egg came out.
Dripping from the nesting box...or dripping into the nest from her as she was laying?
Was the blood coming from her hind end....was there blood on the egg?
'Dripping' as in multiple drips..2-8-20 drips?
Did you check out her vent after she laid?
That's quite a bit of blood on the board and I would assume quite a few hours after she laid. Get a hold of her and take a really good look.
Might even want to isolate her in a wire cage within the coop for a day or two....so you can closely monitor their intake of food and water, crop function(checking at night and in morning before providing more feed), and their poops. Feel their abdomen, from below vent to between legs, for squishy or hard swelling.
Best to put crate right in coop or run so bird is still 'with' the flock.
I like to use a fold-able wire dog crate (24"L x 18"W x 21"H) with smaller mesh(1x2) on bottom of crate under tray.
Then you can put tray underneath crate to better observe droppings without it being stepped in. If smaller mesh is carefully installed, tray can still be used inside crate.