6.5L Peninsular not properly winterized

[fvreap]

I have a commercial fishing vessel with twin peninsular diesels. This is my first diesel boat and I failed to drain the oil coolers. The previous owner walked me through the winterizing process and did not mention this step. The oil coolers have obviously been rebuilt with splash zone and judging by the invoices I found in the cabin, previously replaced and the heat exchangers replaced as well. I don't think the previous owner ever drained the oil coolers. My entire livelihood is depending on these engines and udmarine just unexpectedly went out of business so that's fun. Fortunately I do have 2 replacement oil coolers. Unfortunately I need new heat exchangers.
The oil coolers busted completely open and both of my engines are now entirely devoid of any coolant. I am under the impression that the oil coolers are cooling oil with raw water and coolant is not involved there. Starboard engine heat exchanger is very obviously cracked, it leaks immediately. Port side holds liquid but I do not understand why all the coolant leaked out of port.
Is anyone familiar with these engines and can explain how my oil coolers cracking open caused all the coolant to leak? I did test the coolant before winter with a coolant tester. The port engine specifically I had to cycle up to temp and add more coolant to pass the test. I'm really just having an absolute nightmare of a spring if anyone can give me any mechanical advice I guess that would be nice but I'm s.o.l. on heat exchangers. I guess this boat isn't the dumbest thing I ever wasted 130k on but it's pretty close.