Minecraft server but only 3 hearts?

I have a Minecraft server with my friends, but I only have 3 hearts. Strangely, my friends don't have this problem.

PS: There are also a couple of plugins on the server

This is most likely due to the plugins. Read the description of the plugins carefully and remove the ones that cause the problem. If the plugins aren't the problem, remove them anyway. If that doesn't work, reinstall the server.

/ data merge entity deinName {Attributes: [{Name: generic.max_health, Base: 20}]}

If it still nods, then you have to find the plugin that keeps your hearts on 3 all the time and delete it

Many Thanks!

The command didn't work, but thank you anyway!

With pleasure

It should then be due to some plugin