Looking at the first post. I will warn anyone that may be new here. These descriptions of deficiencies are not always as cut and dry in a few short words. It can take some people a few years to understand the problems they had. In my own personal experience these descriptions have been wrong many times. Let's say your PH is flawless. You can have a deficiency in one thing, and it could resemble what looks like a few other deficiencies. Yet many times what your deficient in, is not a "typical" description of said nutrient. Some people start out and do fine, but a ton of people also fail. In my experience with getting information from online and forums, it hasn't even paled in comparison to time and just personal experiences in learning my own personal problems with this.
I see tons of people giving advice, and unless the person asking for help, has there same exact set up as the helper, down to water types used, soil, nutrients and the exact same Ph tester, etc.; then you should not be asking for much help from the other person. A person cant just say "I grow in soil so I know the problem", which I see all the time, probably from half baked 16 year old kids describing their first grow in Solo cups and using night lights. There are so many other tiny discrepancies that could cause 2 years of failure like I have had (Turned out to be the PH of water used in soil). I'm sure many have found the help useful, much of the time based on a guess. Then there are tons of people such as myself that had to find the problems through trial and error. Even after PH fixing my other problems were fixed through my own tests, many times differing from the vast majority of repetitive answers online or even in books.
Example - Nitrogen deficiency causes yellowing or pale green leaves of entire plant. Um NO. It can start from top, bottom, or middle, and the entire plant does NOT have to show these signs unless gone unfixed. This can look like other deficiencies most descriptions would say is not nitrogen. This is one point of a multitude of problems.
Sorry if I pissed in your coffee. But to the new people that are having problems for extended periods of time. This could be why. Be careful what you take to heart online, because I am certain I am not the only one that has failed through doing this. However if you stick with it, you can get good enough to the point where you look at your plants and know exactly what they need. Personal experience can be for some, a million times better then anything else. I know there are people out there giving up on the idea of there problem being something that everyone else saying it isn't.
I'd like to someday see advanced forums that entail sections just for certain grow set ups. Not like soil and hydro. More like FFOF Soil - distilled water - sunleaves pH test kit - Earth Juice nutrients - Indica. Find your set up!!! A daunting task to make a forum that complex but possible. If someone had my same set up, that's when I would feel confident enough to help them thinking there would be almost zero fault. And this post isn't for the people that have found success online, it's for people that have not. And these could be reasons why.