You might have harder soil than I do @optize. As your tree grows, it might be better for you to switch to 1 GPH heads and put down more of them per tree. There's also a chance that they are putting down more than 2 GPH. You can try measuring their output to see if that's the case. If so, I know that there are pressure regulated emitter heads that folks around here have used.
FYI, my watering time is around 4.5 hours, but I have 3 emitters per tree. That will factor in too as you'll want to spread apart your existing heads as your tree canopy grows, and add more heads. As an example, when your trees get a bit bigger and you add a 3rd emitter, you'll be putting out about 8 gallons instead of 5.3 without changing the duration at all. Since you'll have spread the emitters further apart I doubt you'd have any flooding, but you've delivered more water. Does this make sense ?