Hi. On week 4 of prime trial and have shipped required packages. Everything was good weeks 1-3 and all of the sudden in week 4 delivery speed metrics dropped for one day delivery. Went down to 21% without any changes on our end. Any input or advice? How do we remedy this? We are located in midwest and have a 2:30 pm cut off. Can't do any later as carriers pick up at 4. I feel like we are destined to fail and am not sure if we are missing anything that can remedy. Thanks in advance for any input.