oh gosh, the 1u do-over makes me really nervous - she only got greens on Lantus when up to 3.5u
When you go back to a dose like 1.5 it's clear U-curves, and no obvious rebound #s, so it doesn't make sense to me to lower below the last known dose that was making nice U-curves. The only day really that the curve looks wonky to me is 4/23, and that's more flattish than super-wonky, so could suggest too little insulin.
If it were me I think I would be raising the dose every third day (schedule & ability to monitor for safety permitting), unless there's something I'm missing?