Do a little research on the BBB. They're not impartial and they're not (actually) non-profit though they do file as such.
Basically this is how they work. You own a business. The BBB calls you, sets up an appointment to visit your business, and ask the questions. Then they quote you a price for your "membership" in the BBB and work very hard to sell you on the idea. Regardless of whether or not you join, your business goes up on their website. If you join, you get an A rating. If you don't, you get a lower rating (typically BB, which means they have no reason to believe a customer would have a problem with you).
Keep in mind that at this point, they have no reason to believe ANYTHING about you at all, since they've done absolutely zero research on your business beyond asking YOU a bunch a questions.
Next up, they do nothing. Not a damn thing. They don't research you further, they don't fact-check ANY answers you gave them. They don't do squat. They just go on about their business of trying to coerce other businesses to buy expensive "memberships" in their program. That's how they make their money, after all.
Nothing happens whatsoever until someone files a complaint with the BBB.
"Aha!" you think, "now something useful happens, right?"
Not really.
The Better Business Bureau has no real power, except the threat of a bad rating. Which only matters if you care what the BBB says about you. It's like grammar school: someone says that if you don't do what they want, they're going to tell everyone you eat boogers. Do you care what this person says about you enough to do what they want you to do? Or do you tell them they can say whatever you like, and you're not going to give in to their blackmail?
In reality, what happens next depends mostly on whether the company being complained about is a member of the BBB. If it's a member, the BBB wants them to stay a member, right? They get that fancy sheet of paper to put on the wall of their business that says they have an "A" rating or whatever, and the BBB has a VESTED INTEREST in selling them that sheet of paper every year. (Let's be honest here, that's what the BBB does: sells "A" ratings to member businesses.) The BBB takes the information in the complaint, maybe they pass it on, maybe they don't, but if the customer doesn't keep following up on the issue the business gets the last word and the BBB files the complaint as "resolved". The member business doesn't take a hit on their rating and everyone (except the customer) is happy.
However, if the business isn't a member of the BBB and someone complains about them the BBB probably doesn't send them any information about the complaint at all. And if they do, why would the business waste time fighting over a complaint that wasn't filed directly with them, and involves a business (the BBB) with no actual authority? Typically the business being complained about does nothing because why the hell should they if they don't subscribe to the "Purchasing an expensive wall plaque" service that is the BBB. And since the business doesn't "fight" the complaint, the BBB files it as "unresolved". This hits their BBB rating and thus gives the BBB more leverage to try to strong-arm the business into joining and paying money to improve that rating down the road.
It's a damn scam.
Look at the AN page. There are two unresolved complaints. Two. The only thing that Advanced Nutrients has done to "earn" that F rating is not pay the BBB for an A rating, and not give a shit when someone complained to the wrong company about something. Got a problem with a company? Take it up with them. The BBB is the professional equivalent of "telling on someone" to a random stranger.
Know what's really funny? If you have a complaint with the Better Business Bureau you're completely out of luck. You can't file a complaint against them with the BBB - not that it would matter much if you did since they would just shred it, file it "resolved" and give themselves an "A" rating. That is, if they were even a member of the BBB (which they're not).
Look up a bunch of businesses sometime. See how many are members of the BBB, and how many are not. Now, can you find any non-members with an A rating or any members with an F? Good luck with that. As I said, it's a scam. You pay them money, they tell everyone your business is trustworthy. You don't pay them money, they tell everyone you're shady. It's a protection racket.
