Erin -
Is there anything that changed around the beginning of April? It looks like Gumung was seeing a lot more green numbers especially at preshot times. I've seen this happen if the food manufacturer changed the formula for their food or if the caregiver changed the food.
One thought, if you're not already doing this, is to set up a timed feeder and make a snack available to Gumung at around +8 or +9. You can see on her spreadsheet that her numbers come back into greens after she eats. That's telling you that her pancreas is kicking in and producing insulin which then drops her numbers.