Hi from Cornwall, someone in one of my workshop sessions had a similar problem with cracks on a good bowl. I suggested he apply Pebeo Porcelaine gold / bright gold squeezed out along the cracks, let it dry for 24 hours then fire in domestic oven at, it’s either 150c or 100c for 30 to 60 minutes instructions are on the tube. That gold will stay fast you can put it in the dishwasher too. Pebeo sell these glaze/paints for glass, ceramic and fabric. Hope this help
New glaze note: cracks like that can happen if kiln elements can’t see the center of bowls. Elements need sight line to inside of bowls to avoid cracks like that. It’s radiant heat that needs direct line of sight from elements to inside center of bowls. Learned this in the last couple of years. No glaze cracks since changing shelf heights
Are you still experiencing pinholing? Someone recommended holding at the top temp for 10-15 minutes to allow the glaze to run into the holes. I haven't tried it yet. I have a manual kiln, but I'm going to try it this round.
