Hi Sandman89, welcome!!
A few things stick out to me and I'm sure others as well. Just a quick review of the 3 new cards you acquired (Congrats on that!) shows that you would want to start with; Paying down your utilization and gardening for a while (letting the inquiries, new cards, and average age of accounts grow.) . Here is the breakdown:
BoA Platinum Plus - $1,600 / $2,500 = 64% Utilization
BoA Cash Rewards - $200 / $1,500 = 15% Utilization
Amazon Store Card - $0 / $1,200 = 0% Utilization
Total Available Limits - $5,200
Total Overall Utilization - 34% Utilization
Your overall utilization ultimately should fall below 28.9% as should the individual card utilization. Preferably however, you'd be best served having 8.9% utilization on any individual card or lower. You would definitely want to pay down the BoA Platinum Plus sooner rather than later. Being all 3 of these cards are new, your age of newest account and all accounts has taken a hit, hence the scores will too. This is temporary, but time heals all 
. In regards to the authorized user, and perhaps someone else can help here, but it's good you removed yourself as that utilization was very high.
@Sandman89 Welcome to the myFICO forums!
Ultimately, what a person needs to improve their FICO scores and build credit are three open credit cards (secured or unsecured) in good standing and one open installment loan in good standing such as a car, home, student, personal, share secured, or credit building loan. This combination is what the myFICO score theorists here have determined is what you need for optimal credit building and FICO score. You can have more CCs and more installment loans, however, this will not increase your FICO scores.
Next, (this is only important if you are attempting to purchase a large ticket item like a home or car) is paying in full all of the credit card balances each month, before the posting date, except one. This is called the All Zero Except One (AZEO) method. The one credit card you allow to post a balance needs to be less than 8.9% of the credit limit of the card. So using one card each month to buy lunch, letting it report and then paying in full will maximize FICO scoring. Keeping your utilization of your cards below 28.9% both individually and collectively will prevent you from getting a FICO scoring penalty.
The installment loan will have its greatest impact on your FICO score when the amount owed is at its smallest such as a few months before the loan is paid in full. If you don't have an installment loan you can check into SelfLender or a Share Secured Loan at a Credit Union.
Keep in mind, building credit is a marathon, not a sprint. It involves demonstrating to a potential creditor that a person can handle credit responsibly. If you have open, active accounts that are being paid on time and pay all of your bills on time all the time, apply for credit only when you actually need it and use credit cards sparingly maintaining low credit utilization, then you’re going to earn and maintain great credit scores. It would be impossible for you not to do so. This is the fastest way to build good, solid credit.
I think the advice given above is your best game plan. Give it some time, work your balances down and as your scores go up, other cards will open. For now, it would be best to garden and let the inqs age and fall off. As far as the AU impact, as your own AAoA grows, the impact of the AU will decrease.
6 months is a nice amount of time since it puts more distance from previous apps
Welcome, @Anonymous.
For Chase, wait until your oldest card is a year old. Also, before applying, build in a period of gardening (not applying for anything). Three months of gardening is OK; six months is better.
Also note that you'll eventually have Chase's 5/24 rule to contend with. If you've opened five or more credit card accounts within the past 24 months, denial is likely. You're at 3/24 right now.
If getting two Chase cards is your priority, don't apply for anything else in the meantime. You can get your first Chase card when your oldest card is a year old, then apply for your next Chase card about six months later.
A middle ground would be to grab another card somewhere (after appropriate gardening), then grab your first Chase card when the time is right. You can grab your second Chase card when you're back under 5/24.