Unable to explain afternoon high

I was diagnosed LADA 4 years ago. I take Pioglitazone before breakfast,
Metformin 500mg and tenegliptin before lunch and
Metformin 500mg before dinner

My breakfast is average 15-20g carb (avocado toast and berries, no flour banana pancakes) and my 2 hour post breakfast readings are always < 120
Even when I once last week had 50g carb breakfast, I had 2 hour post lunch 145

But my lunch story is different. My average lunch is 25-30g carb, low fat and low protein. I take a 1.5 mile walk 1 hour post lunch. But my 2 hour post lunch readings go up to 220 and today it went 255!

I can’t explain why? I had 25g carb and a nice 40 min walk

My doctor hasn’t advised insulin yet. Please help me control my afternoon highs. My past 2 A1c have been 6.9 and 7.1

Your lunchtime protein is broken down and producing glucose (just like carbs). T1D’s on pumps or injections bolus for this, depending on the protein eaten it converts to 50% or more carb equivalent (50 grams of protein produces the equivalent of 25 grams of carbs)

Different types of proteins take longer or shorter to convert to carbs, depending on fats and other carbs eaten at the same time. Some proteins might not produce glucose in bloodstream for 3 to 6 hours following meals.

Sorry for the confusion, I meant lunch has 25-30g carb, low amount of fat and Low amount of protein

If you are LADA, its possible you have less and less insulin from pancreas, and adding insulin may be needed. Possibly reducing some of the other meds.