PV=nRT - Ideal gas law, n and R are constant, linear relationship between P, V and T. With V (volume of the football) assumed constant, the relationship between the pressure at two different temps is given by
P2 = P1(T2/T1) where T is the temp in Kel
Given your starting P of 12.5 psi and your Kelvin ratio of .94, I get:
P2 = 12.5 psi x (.94) = 11.75 psi - not 10.9 psi
The temps look off too. Room temperature is 70F and ambient air temp on the field was about 50 F .... roughly 21 and 10C respectively. If they were inflated at 12.5 psi, this would translate to a decrease of about .4 psi to 12.1 psi. Gets you part of the way there but not the whole story.
The balls were wet, and there was wind, so the surface of the ball would experience some evaporative cooling (assuming they were measured on the sideline), but probably not enough to get you to the delta T to explain the difference, if they were in fact starting at 12.5 psi or higher.
We will need some more facts to figure out if temp was a significant contributor or not.
Rich