Unfortunately for you, you can't transfer funds between HSAs.  But you do have a couple of options available, and how  it's handled depends on whether you've already filed your 2018 tax return or not.

If you haven't filed yet for 2018, you will want to remove the excess contribution(s) before the filing deadline of October 15.  You'll need to contact the bank or financial institution that manages your HSAs to request the change.  Tax documents will be issued to reflect the withdrawal of excess contributions.  If you wish to continue to have a separate HSA, you'll need to divide the max contribution by half for each calendar year, and deposit only that amount into each HSA.

I found an article that explains the process (and options) much better than I could if I went into detail here.   The article is from 2016, but the procedures remain the same.  I'm linking the article below.  Hope it's helpful to you and will clear up how you need to proceed.

https://www.hsaedge.com/2016/11/06/how-to-remove-excess-contributions-to-an-hsa/

Sort of, but it depends on what you have already done.

First, you cannot withdraw the excess without penalty past the due date of the return. As Kat noted, IF you filed for an extension, then the due date is October 15, 2019; otherwise, the due date that you had to beat was April 15, 2019.

If, by chance, you did not withdraw the excess in time, then the total amount of the excess is put into Other Income (line 21 on Schedule 1) and you pay normal income tax on it. Whose HSA is dinged for the excess depends on how you answered TurboTax when it told you that there was an excess contribution and which HSA has the excess (could be both).

Let's pretend that TurboTax told you that your excess contribution was $7,900 (but more on that later because that's actually not right), and that you said that the entire excess was due to your HSA. This creates a carryover of excess contributions for you (if you did not withdraw them) to 2019. In 2019, the carryover will be applied to your HSA as a "personal" contribution. If you make NO OTHER contributions in 2019 to either HSA, then the amount carried over will be taken as a deduction in 2019, thus reducing your income again. In short, the only downside is that you paid a 6% penalty and got the deduction a year late.

That is, you contributed the $7,900 in 2018 to your HSA, it's still in your HSA because you didn't withdraw it, but you didn't get the deduction until 2019. This is absolutely not obvious, so please ask questions if you need to.

NOTE: if you have a carryover, TurboTax will automatically apply it to the next year. Therefore, you must reduce your normal HSA contributions to keep the total amount of the next year's contributions under your limit. Otherwise you just perpetuate the excess and get dinged 6% again.

NOTE NOTE: if you are both 55 or over and both have HSAs, then the actual 2018 limit was $8,900, not $7,900. The catch is that you both get the $1,000 "catch-up", but the catch-up must be contributed to your own HSAs. The remaining $6,900 can be divided up any way you like (like putting it all in his as you did).

So while your husband could have contributed $7,900 to his HSA, you still should have been able to contribute $1,000 to your HSA. In fact, you could divide up the $8,900 anyway you like between the two HSAs, so long as each HSA gets at least $1,000.

Since I don't know what you have actually done to this point, I can't be sure of the best advice, but please come back and tell me where you are at return-wise, and we'll figure it out.

When you say that you are both over age 55, I assume that you were both age 55 or over in 2018 and both were eligible for the $1,000 catch-up contributions, each to your own HSA account.  With each of you contributing $7,900 to your respective HSA accounts for 2018, you have a $6,900 excess contribution for 2018 between the two of you.

If you timely filed your tax return or requested a filing extension, as others have said you can correct the excess by obtaining explicit returns of contributions from the two HSAs totaling $6,900 (with the amount distributed being $6,900 adjusted for investment gain or loss), with the excess allocated between the two of you any way that you wish although it probably makes sens to keep things simpler by allocating the entire excess to only one of you.  Any investment gains distributed with the returns of contributions will be subject to ordinary income tax on your 2019 tax return. Generally this would be preferable to carrying the excess into the 2019 tax year.  If you allocate the entire $6,900 excess to your own HSA account, you can use the amount returned to fund a 2019 contribution for either you or your spouse (or anything else you want to do with the money).

Note that only actual excess contributions are permitted to be distributed as a return of excess contribution, so you are not permitted to obtain a return of $7,900 since only $6,900 of the total of $15,800 contributed is excess.

If you choose not to obtain a return of contribution, the excess $6,900 contribution will need to be allocated between you and your spouse and 6% paid as excess contribution penalty for 2018 and the excess(s) will be carried into 2019.  You would than be able to contribute the excess allocated on your 2018 Form(s) 5329 for each particular HSA as part of a contribution for 2019 to the respective HSA.  (If you end up being ineligible to make the contribution for 2019 and apply the excess, it can become costly to not have simply obtained a return of excess contribution for 2018 since the excess can only then only be resolved by making a taxable distribution, which subjects the amount to double taxation, and, if under age 65 at the time of the distribution, to a 20% early-distribution penalty.)