The commit fees are changing.
If/when mempool fees are fluctuating, also the commit fees will increase or decrease and that will be affected in your channels "can send".

• https://lightningwiki.net/index.php/Fees
• https://bitcoin.stackexchange.com/questions/89232/why-is-my-spendable-msat-much-lower-than-msatoshi-to-us/89235#89235

Another aspect that you should take in consideration is the "buffer" kept in each channel when is about to be depleted:
https://github.com/lightningnetwork/lnd/blob/6dea86428d031171af30119e3f6599820dc5454a/lnwallet/channel.go#L3803-L3815

For those cases, if you really want to empty that channel, you have to go slowly with smaller amounts, going closer and closer to the last sat you can send.
But with Alby Hub you cannot select a specific channel to make a payment (yet). You will need to use another node management software like Thunderhub, RTL, or Zeus that allow doing that.

Is something wrong with my LND?
Should I be worried?

No. This is how LN it works. That's why we always recommend to NOT open small tiny channels where this difference can be seen easily. For a larger channel it will be insignificant change.

You might be interested in reading Rethinking Lightning if you're really interested in the details:

Channel liquidity is a problem, but it is also deceptive. When you have 100k sats of inbound liquidity you would think you could receive up to 100k sats, but this isn't the case, often you can't actually receive any. This is because of on-chain fees, when a payment is being made in lightning you are creating pre-signed transactions that have outputs for every in-flight payment, these outputs cost potential on-chain fees and the high on-chain fees go the more it eats into your liquidity. After we've solved most of our force close issues Mutiny this has been number one support request. Even if you do everything right, understand liquidity and have enough for your payment, sometimes it still won't work because on-chain fees are too high. This is always really discouraging because isn't the whole point of lightning to not have to pay on-chain fees? Fundamentally, all current lightning channels could become entirely useless if on-chain fees went high enough because a single payment would require too many reserves. Obviously this is hyperbolic, but I hope I am getting the point across that on-chain fees don't just effect the opening and closing costs of channels, even if you are a diligent node runner that only opens channels when fees are low, that is not enough, your channels need to be large enough to pay for the on-chain fees of each HTLC at any future on-chain fee rate. As on-chain fees go up and up this problem will only get worse.

Great choice of channel peer ;) !

I remember having this exact question when I started on the Lightning Network.

We answer that question here: https://rizful.com/docs/balances-and-capacities#outbound-capacity ... under "But why does my outbound capacity keep changing slightly?"

Have you checked for onchain fee changes during 130 and 131?
Some hours ago there were some oscilating onchain fees.

The balance on LND (and therefore) RTL will be calculated by LND taking into consideration the current onchain fees, and they have been oscillating a little bit today, for example block #874115 had fees up to 855sat/vB, while block #874116 had fees up to 262sat/vB.

Best,
Jean-Paul
Alby Support Team
getalby.com

I find that NWC is really easiest to use on Alby hub. A lot of this is such a mystery to me.