Higher speed films like Tri-X usually prefer a little more than 1 hour. Simon is also right Rodinal is one shot reuse won't work. Temp below 18C reduces the developers activity. . With your inversion regime the film should be overdeveloped not underdeveloped. Furthermore what you did was not stand but semi stand (you inverted the film for the first 10 minutes and more often then the norm for stand, stand from 8sec - 1 minute max continous at the beginning, maybe 3 times at half time). Could you post a non inverted scan of the neg, maybe there is a problem with your scanner.