Thanks all for the advice!
We think the problem was from the heat, but not just from outgassing – the heat in our workspace was high enough to cause the epoxy to cure before the slight patterns left by our rollers and tipping brushes had time to settle/flow at all (eg the viscosity of our epoxy was too high due to the heat). We were able to fix the problem by applying each coat either very late at night or very early in the AM, which also helped with the bubbles from outgassing.
Thanks again all for the troubleshooting and feedback! Really appreciated!