No offense taken. I have lots of experience keeping white clouds and 4 in 1 gal is a tad much but I know what signs of stress to look for and I am quite confident that the fish will remain healthy.
Normally I wouldn't suggest more than three in 1 gallon of water... I mean 1 gallon of actual water not just a 1 gallon vessel. My water volume is just over a full gallon of water. When the plants fully grow in their mass will make it slightly less than 1 gallon.
however, I change more than 50% of the water every week and as I said, am very experience with the fish and its behaviors so the fish are in good hands.
I actually had 5 in here originally and it took only a couple of days to see that wouldn't work well. I had 1 male that was particularly boisterous and clearly the vase was too small as he chased the others incessantly. After removing him the remaining four fish immediately relaxed and swim about quite actively and playfully.
The two things you need to consider and keep constant attention too are:
1. the activity level of the fish. White clouds tend to be active but are often quite content to dart about each other in a circle. Just make sure you tank can accommodate the size of their shoaling. Mine does with 4 four... Three in a 1 gallon is almost always doable.
2. water quality. Since this should be a consideration in every tank I wont go into details on this.