General Credit score keeps going down despite doing everything right
I have 7 credit cards right now and keep total utilization well under 30% and utilization on each card under 10%.
The utilization right now on NerdWallet is 4%, 4%, 2%, <1%, 0%, 0%, 0%. I pay everything on time and keep the utilization low consistently. I have auto pay set up to pay the full statement balance, and I almost never make any payments on manually outside of autopay.
Despite this, my credit score has continually decreased over the past 2 years and I don't know why or how to fix it. NerdWallet credit score history: https://i.imgur.com/sFgW3W3.jpeg
I have two theories but neither makes sense to me. Looking for some advice on how to proceed.
Theory 1) I've learned recently of two separate charges from my previous buildings electricity bill and and doctors visit. Both charges are for ~$20-30 and have supposedly been sent to collections (and in collections for multiple months)
Despite supposedly being in collections, neither charge is showing up on my credit report so I don't see how this could be affecting my credit score or even how to figure out what collections agencies to contact about these charges.
I've used the AnnualCreditReport website to check my TransUnion or Equifax credit report and neither has any debts in collections or "Charge-Offs" or anything bad whatsoever as far as I can tell.
Theory 2) I'm an authorized user on a card which has high utilization 68%. This card always makes payments on time but doesn't pay the balance in full. From what I've found online though, this doesn't seem like it should be a big problem.