tajoch,
I would say that the heat is to be expected under the circumstances. 50% of 30 is 15A and you even have some over that.
If you can change these wires to #10s or remove half of them you should be Ok.
If you want to try an experiment take the bulbs out of 1 or 2 fixtures on each of the circuits and see what happens to the Temp of the conduit.
Bill
