I have two groups of people, each group taking a different blood pressure medication. Blood pressure is taken daily for 30 days. Medication 1 works better than 2, as is shown by a lower 10 mmHg difference on day one. It is also more stable so blood pressure remained the same over time. Patients had tolerance to the second medication, and over time around day 20 blood pressure begins to rise again. Since they both work in lowering blood pressure initially, the 10 mmHg difference in the beginning isn’t a big deal, it’s the larger difference of around 30 mmHg by day 20-30 I am interested in. The delta between the two groups was calculated at each day (increase in delta was seen at days 20-30). I want to compare the delta between groups at each timepoint to the initial timepoint. What tests should I use?