Personally, I would check very carefully for the presence of mold... maybe pulling off some brown leaves; if it's resistant and doesn't come off, you'll feel more at ease. From the photos, I can't be precise, but if you rule out mold, it could be a deficiency. But as grandma said, you still have little time, so correcting it would be pointless. One last thing, you can also do a bit of defoliation just to let the air circulate even better.