yellow water with a strong iron spell

We bought a water heater that was used for 6 months and then the buyer didn't like it, so the plumber took it back and it sat for an unknown amount of time until we bought it and had it installed 2 weeks ago. At first the water had a brown tint, so my husband drained the hot water heater and now the hot water has a yellow tint and a very strong iron smell. Could the tank be bad because it sat unused for an unknown amount of time? Our plumber ordered a new anode rod and said to flush the tank again. Will this really fix the problem??
Thanks! Twitty
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