When the world generates or when you plant a tree and then leave the game (once nobody else is in it) the trees turn into vanilla trees

Could it be because I have a few other mods in the server?

That just looks like normal perspective.

I’m a bit confused at how you managed to plant a tree on sand in the first place?

If you want more help on this you’re going to have to provide a mod list, though this is a strange issue and I can’t see how another mod would be causing it.

I see no evidence that you're running Dynamic trees at all.

if you look closely there is an tree in the background with a log slightly bigger than the other

I see no evidence that you're running Dynamic trees at all.

I'm closing this due to inactivity and insufficient info. If you or anyone else still experiences this problem and can provide some more context please comment/re-open.