People are so weird.

If you give your baby solids like one week or day before their sixth month birthday you've committed some kind of atrocity. Hey guess what? In ten years and even less, no doctor or anybody is ever going to ask when you fed your baby solids, that week or even month won't make a difference. Any kid can have gastrointestinal issues no matter what. And a lot of studies (since people are so caught up on studies) do say that the "leaky gut" is just a theory. So it's a reccomendation to wait, but you're not gonna kill your kid if god forbid you feed them solids two days before they're 6 months. I'm waiting until then, but I have friends with babies who have already started, and I don't question them on it or ask them why, or try and "educate" them because I think I know better. It's their baby, not mine. If they're about to give their baby honey (which is potentially fatal) then yeah I'll say something. But if they wanna give some rice cereal to their baby for whatever reason, I'm not about to start lecturing them on it. NO ONE LIKES UNSOLICITED ADVICE. 
No college is going to question your child on if they were breastfed or formula fed or if they started solids too early. Or if they were left to cry it out for a few minutes or not. No one is going to care. At all. It will be completely irrelevant. I don't even know when I started solids or if I was breastfed or not or if my parents let me cry it out. It has never been important. We're all different and we all (generally!) turn out healthy no matter which direction our parents take!
Now obviously I wouldn't feed your baby cake and ice cream or hold them to sleep till they're 12, but seriously everyone needs to RELAX.  
People get so worked up because they read shit on Facebook or google studies (or don't even bother to look into the credibility), that are CORRELATIONAL (which doesn't equal causation), and think they're experts and are suddenly SUPER involved with how you're raising your own kid. You all just do way too much google research. If someone's pediatrician with years and years of training and education tells them something, I think they're okay to believe them over something you read online. 
If everyone could just chill and let people do things differently for their babies within reason(obviously) that'd be great. Because everyone is doing the best for their kid and like I said when your kids an adult none of this will be relevant. So just calm down and stop telling other people what they should be doing, and start focusing on your own child and your own life, ya freaking sanctimommies.