weird behavior after wc

[mahi]

My betta is living in a 4 gallon cycled, planted tank together with a nerite snail. I have been changing 20 to 40 % of the water each weak. Water quality never seems to have been a problem. I've been testing the water pams before each water change and they were always:

Ammonia: 0
Nitrite: 0
Nitrate: <10
pH: 6.8

The temperature is at 79 atm.

I'm going away for 6 days tomorrow and wanted to do be super save and changed 90% of the water yesterday. Additionally, I thoroughly vacuumed the gravel and removed some algea from the plant leaves. I think that was a mistake. Today my bettas fins are clamped and he seems to swim around more then usually. He is still eating, though.
The snail also seems less active than usual (and the snail poop might have changed color- I'm not sure).

I'm not sure what to do? Should I change the water again, in case I brought in something toxic with the last water change? Or did I stress the fish too much with such a big water change and it's better to leave it alone?

I just tested my water and all the params are exactly as described above. I could really use some pointers, especially since I'm leaving tomorrow morning.

[mahi]

Just found the sticky and thought I will answer:
What size is your tank? 4 gallon
What temperature is your tank? 79
Does your tank have a filter? yes
Does your tank have an air stone or other type of aeration? yes
Is your tank heated? yes
What tank mates does your betta fish live with? one nerite snail

Food
What type of food do you feed your betta fish? betta pellets
How often do you feed your betta fish? once a day with one fasting day per week

Maintenance
How often do you perform a water change? weekly
What percentage of the water do you change when you perform a water change? 20 - 40%
What type of additives do you add to the water when you perform a water change? none

Water Parameters:
Have you tested your water? If so, what are the following parameters?

Ammonia: 0
Nitrite:0
Nitrate:0 -10
pH:6.8
Hardness:
Alkalinity:

Symptoms and Treatment
How has your betta fish's appearance changed? clamped fins
How has your betta fish's behavior changed? swimming around more
When did you start noticing the symptoms? today after big water change yesterday
Have you started treating your fish? If so, how? no
Does your fish have any history of being ill? no
How old is your fish (approximately)? maybe half a year? I got him 3 months ago and he wasn't fully grown then

[homegrown terror]

a lot of bettas act weird for a few hours (sometimes up to two days) after a total or almost-total water change...something about not being able to smell themselves in the water and thinking they've gotta claim a new "territory" is the explanation i've heard the most.