Hello,
Before asking credit-newbie questions, I'd like to thank those who have contributed to the information base on this forum. It's early in my credit journey, but I've already found this forum to be a valuable resource. I plan to follow the share secured loan method described here to add an installment loan to my credit mix, for example (after allowing my last inquiry and new account to age a bit and doing more research to make sure it would be a good option for me).
I've been building credit history since January and first registered for MyFico in June (after 6 months of my own credit history, not counting the account on which I'm an authorized user, which brings me to 13 years). At this time, my scores were reporting in the high 760s. The most dramatic decrease occurred at the end of June, with smaller decreases since then.
Right now I find myself seeking clarification about the incremental decreases in my scores. In terms of negative changes since June, I've had an inquiry and a new account (both related to a rental agreement, both updated in July). Other than that, I've had a solid history of payments, CLIs on both my cards and low utilization (always around or below 7%, though it's flucutated). This leads me to wonder if the changes are partially utilization-related, in addition to the inquiry and new account (due to too-low utilization, as declines have correlated with 0 balances being reported; then again, having small balances report instead didn't reverse the trend) and thus if my credit limit increases could be hurting me further.
When my scores dropped from the high 760s to the 730s at the end of June and one of the reasons reported was that no recent balances were detected, I thought the issue was that I paid off both my cards before the statement dates. I left small balances (under $16) on my cards at the end of July, but saw a further decline in my scores even though I was approved for a CLI for my Capital One card that month. This was also the month I had the inquiry and new account added, but the days I received alerts about those there were no score changes reported.
In August I followed some advice I saw here to leave a small balance on one card only, thinking part of the problem that month was that I went from 0 cards to both my cards reporting balances. When the balance on my Capital One card reported as slightly less than the month before (think $10 instead of $11) at the end of August, I saw an increase with TU and EQ. However, both scores decreased again in a few days when that card was reported again to show a 0 balance after I paid it off (after the statement date). A few days later when my other card reported with a 0 balance, I saw yet another decrease.
Today I received an alert showing that my scores had declined by 14 points, this time with all 3 bureaus (which is disappointing, as my EX score had been the only one that had seen no decreases for the last few updates); the only comment noted that a credit limit increase for the CC I have with my credit union had been detected. Maybe the CLIs were a bad move; I only requested them to help my scores. I'm not sure if they're hurting me further (see above) or if they will eventually lead to positive changes and it's too early to tell.
The only other factor I can think of is that the utilization on the card on which I'm an authorized user fluctuates, but it's never been over 10% and I received the comments about "no recent balance history" when that card was reporting a balance.
Now I'm wondering if I'll see a decline yet again at the end of September if a balance increase is reported on one card (both are reporting with 0 balance now; I didn't think my payoff with Capital One would be reported almost immediately and my intention was to leave around the same small amount reporting each billing cycle, per the advice I've seen). I may try having my other card report a small balance instead for the next few months, as I've only seen that card's balance reported once per month.
It has also crossed my mind that the significantly higher scores reported in June were due to some sort of fluke. At least the decreases since then haven't been as steep. Any suggestions that will put me on the path to an upward trend in my FICO scores would be appreciated. 
Information on my history:
Inquiries: 2 from January, one from mid-July
Accounts:
Capital One secured CC, started January (initial credit limit: 450. increased to 1950 in July)
Secured CC from a credit union, started January (initial credit limit: 500. increased to 1000 in August)
Lease, added at the end of July (related to the inquiry in July)
Authorized user on a CC open 13 years
No missed payments, etc.
Hello and welcome to the forums!
From what you suggest you have a new file and scoring is going to be a little wonky as the report is busy... especially if it required a HP to add to that CU card.
Long term simply never miss a payment and never pay anything late or less than the minimum and you'll be fine.
Short term, just talking FICO optimization:
Pick up a third card, doesn't have to be right now but you're stuck in sort of a no win situation with 2 cards under many of the FICO models; you want 3+ and I strongly suggest 5 (or more if it fits your needs) is where you want to be eventually just from the way the revolving utilization portion of the algorithm works and how some lender underwriting historically has been though this is less of a factor now.
The share secured loan trick likely won't be immediately beneficial as you have a lease, but it's an easy low cost tradeline to maintain worst case but with installment history already on the report it won't be a major impact... though I would suggest having 2 installment lines doesn't hurt anyone.
End of the day you're doing fine right now, and ignore the random small ups and downs as various balances report or $0's report: with a longer hsitory and more tradelines that'll smooth out to a more steady state and ultimately those swings will be small and not a big deal... can always pretty up your report before you want to apply for something new as long as your spending isn't outstripping your financial capability.
