If you cannot use conventional herbicides in Ontario...perfect lawns are going to be nearly impossible...clearly the iron compound is not doing the job. Don't give up--it may take repeated treatments or getting the timing just right. Some weeds are killed by short mowing and some are killed by frost. But the ground ivy will persist through both of those.
I suggest reseeding or overseeding with one of the Canadian dense sports-type Kentucky bluegrasses, like Quantum Leap or Touchdown. The ability to compete with poa annua as claimed in their advertising, is a good sign.
The best types of fine fescue are also very dense. Perennial ryegrass is not particularly dense.
The best bluegrasses are competitive and crowd out most weeds, especially at high fertility levels. Keep the fertility levels at the maximum recommended in your town, (probably 5 treatments per year--using 50 percent slow release nitrogen). Irrigate regularly to avoid thin spots due to dryness.
Better still, resod with a top-quality bluegrass sod of a type that has grows tight, and has great density and competitive ability.
The reddish weed in the new grass could be a summer annual, a type killed by frost--or killed by just mowing at 2 inches--hopefully not a major weed. Tall weeds do not withstand short mowing.