Usually, the sodium doesn't cause you to retain water unless it is paired with higher carb foods - i.e. chips, pretzels, etc.

You have already identified the next top potential culprit in dairy. I wouldn't worry as much about the butter, but the cheese could possibly be the issue.

The next most likely culprit may be nuts. Many of us significantly increased nut consumption when moving to this WOE. Where small amounts now and then may have never caused an issue, eating more on a regular basis could be having an effect.

Of course there is bio-individuality so you could be part of the small percentage who is actually sodium sensitive and need to keep levels lower than the rest of us.

It's also a possibility that it's not the sodium in the enhancer..... what else is in it? Some are affected by artificial sweeteners or certain food colorings or flavourings.

Have you just started keto? You have only 5 days eating history in your recent food diary so I'm guessing "new" or perhaps you tracked elsewhere.

What besides a 1 pound fluctuation on the scale indicates water retention? Are your legs/feet swelling? My weight fluctuates daily and sometimes more than a pound. This is common for the masses whether "dieting" or not. It is what the body weight does. Some find using a weight trending app to be useful showing the overall up or down trend, minimizing the daily fluctuations. Try Trendweight or the apps Happy Scale (iphone) or Libra (Android) if you find yourself too focused on and influenced by the number on the scale.

I don't know what is in Imperial margarine but if it contains trans fats it would be beneficial to eliminate it from your diet. It's the 1 fat most experts (possibly all) agree should not be eaten.

Yogurt? Many are able to fit plain Greek yogurt into their carb amounts. The fruity/sugar flavored stuff, not so much. Some people are lactose intolerant or just don't like yogurt so don't eat it. Some have found dairy stalls their weight loss but that usually takes some time to determine. If you enjoy Greek yogurt and it fits into your daily carb amount it can be keto friendly.

My experience: I use butter, avoid trans fats, enjoy/eat plain Greek yogurt. I have no sodium sensitivities that I'm aware of and need to hit amounts ~3000...generally speaking but the low end of the common keto range of 3000-5000 mg is generally enough for me.

Sodium is supposed to help you retain water.
Keto is a naturally diuretic diet and requires 5000-7000mg of sodium a day.
You’re nowhere near where you should be.
You’re probably so deficient that when you begin to get close to what you need your body is holding onto it as much as possible. Because that’s what it has to do when you’re deficient. And it cannot let go of excess water in a sodium deficiency because that’s dangerous.
If you consistently get the sodium you actually need, your body will finally regulate it naturally and won’t hold excess water because it won’t have to.
You really can’t get too much sodium unless you have a specific health condition that affects your renal handling of it.
Don’t restrict sodium otherwise.

I should have said that I shoot for 4000 mg in logged foods. I liberally salt food as well.

I also don't think you are getting enough