I would say yes ,as I do not know when was the last time you checked the coolant,but it had to go somewhere . and if it is discolored I would guess it is mixing with the engine oil, figure it out first ,do not just refill the coolant.
Case used normal ethylene glycol, yellow hd diesel antifreeze.
Diagnose the problem.
Depending on the circumstances, flush/change coolant system, check oil, pressure test coolant system.
May be a big problem internally or a simple severe lack of maintenance.