Identify the scope and timeline of the issue:

Understand if this drop was sudden or gradual. If it's a sudden drop, it could signify a recent major issue, such as a system failure, supplier issue, or a drastic increase in demand.

Segment the data:

Break down the fulfillment rate by various dimensions like regions, time of day, type of medication (prescription, OTC), type of delivery (same-day, scheduled), etc. This can help identify if the drop is across the board or localized to certain areas.

Check internal operations:

Assess different points in the supply chain, from the point of order placement to delivery. This could include the inventory management system, the process of picking and packing orders, the courier services, and the delivery tracking system. Internal factors could include technical glitches, stockouts, logistics issues, or manpower shortages.

Review recent changes:

Investigate if there have been any recent changes to the product, operations, or policies that could have affected the fulfillment rate. This could include changes to the website or app, new delivery policies, or changes in delivery partners.

Consider external factors:

This could include increased competition, changes in regulations, or larger events such as strikes or natural disasters that could affect the delivery process.

Look at related metrics:

Check if other metrics have been affected, such as order volumes, customer complaints, delivery times, etc. This could provide more insight into the problem.

Engage with cross-functional teams:

Collaborate with teams like operations, customer support, engineering, and logistics to understand the problem from different perspectives.

Formulate and test hypotheses:

Based on the gathered insights, form hypotheses about the potential root causes of the problem. These hypotheses should then be tested with further data analysis, customer surveys, or possibly experiments.

Plan and implement solutions:

Once the root cause has been identified, develop a plan to mitigate it. This could involve fixing technical issues, adjusting inventory levels, changing delivery processes, or improving communication with customers about delivery expectations.

Monitor the results:

After implementing the changes, closely monitor the fulfillment rate and related metrics to see if the situation improves.