As far as I know these things have some truth behind them, but are a possibility. My 3 year old started solids at about 5 months, & needs to go to a speech therapist. I think it's just the chewing that develops their jaw, but they don't really chew on things til they are 9 - 12 months anyway.
I think the low iron levels are after they are on cows milk. Formula has what they need in it. Once they are on cows milk though they need other foods to give them what they need.