Hi DW,
K1 could easily be a relay instead of a contactor (cheaper) as the control element in my drawing, K 1-1 and K1-2, are 2 pairs of contacts on the K1 relay, K2 is a 3 or 4 pole contactor which has the stat or cutout in series with the control coil.
I had cut this drawing down to it's most basic skeleton, the OP could have used extra contacts on the start/stop relay for status indicators and the like.
I had initialy assumed the OP was controlling both heaters from one stop/start circuit, but then he wanted to control both heaters seperately, hence the mention of three contactors initially, revised to four, to give independent control to each.
Half the trouble I had was the actual drawing with the software package (Tinycad), as Iam not used to drawing in software.
This was the circuit for one heater, as I said he would need to duplicate this circuit (apart from the E-stop) for additional heaters.