That BG of 56 that is mentioned was 1 week ago.
So yes, a dose increase to 1.75U, based on the curve done today, is the right move to do with lantus for kitty Jasmine.
In fact, the 1.5U dose has been held a really long time, and there may be a bit of insulin resistance to break through.
In other words, Jasmine may have gotten used to those high numbers, and a dose increase can help to bring those BG levels down to a more reasonable number. Jasmine needs to see some greens at mid-cycle.
Lantus is gentler than most insulins. Might not always have a nadir at +6 either, so testing either side of that time is helpful. A +5 one cycle, a +7 another cycle. Wink's nadir was very early, around +3 to +4. ECID Every Cat is Different, so you need to test to see the response of the insulin for YOUR cat.
We don't recommend that the insulin dose be held for longer than 1 week, unless the BG levels, the nadirs, tell us the dose needs to be held for a bit longer.
Dosing protocols for Lantus are in one of the sticky threads at the top of the lantus forum. There are guidelines there, for both SLGS and TR dosing methods.
All those sticky threads in the Lantus forum are good reading for a caregiver using lantus (or levemir) for their cat.