30 km Training Run

Erratic heart rate right from the very start, though didn't feel tired. About the same time then a slight pain in my left ankle, though that didn't last long and didn't cause any further problems. During the first 10 km stomach uneasiness, just had to find a toilet, which I did at the 10 km mark. Diarrhea no less (that will teach me to have hot Mexican pizza the night before a long run). I'm wondering whether this (diarrhea) was the cause of the erratic heart rate as it settled down after this. Well the run was from home to Werribee River and return. Total distance on my Garmin Forerunner 30.75 km for a time of 2:43:14 which equates to a pace of 5:19 mins/km. During run consumed PB Gel every 30 mins, took 5 packets out with me and water. Consumed all of them. Checked weight on return, weighed in at 77.2 kg a loss of 2.5 kg. Weight on first getting out of bed was 79.7 kg. This equates to 3.14% fluid loss (not sure if this is acceptable or not). This is probably higher than it should be as I did have that toilet stop.