good morning everyone i recently transferred over from Usmc to NG to do Rotc. I am a fit guy like high PFT, CFT; army equivalent to ACFT. Never fell out of rucks either. However today we did 6miles and i did do terrible(like 15:30per mile) idk why could of been dehydration or humidity. I don't wanna give excuses but how do i get better? My 3mile time is 19:40 and last ruck i did with the Marines was the 20miler under like 6 hours with 55lbs. Which has been over a year. I do lift weights and keep fit any advices?