DataStore saved my data as someone elses?

So i went into the live server to test the game with my friend and we were playing for a bit, and then we got off.

We then got on later and we both had the same stats!

Not sure what is going on, if you want to look through my datastore setup here it is.

--Variables
local leveldata = game:GetService("DataStoreService"):GetDataStore("level")
local EXPdata = game:GetService("DataStoreService"):GetDataStore("EXP")
local xpLeveldata = game:GetService("DataStoreService"):GetDataStore("xpLevel")
local Golddata = game:GetService("DataStoreService"):GetDataStore("Gold")
local toolsdata = game:GetService("DataStoreService"):GetDataStore("Tools")
local HttpService = game:GetService("HttpService")

function savedata(dataname, playerid, value)
	game:GetService("DataStoreService"):GetDataStore(dataname):SetAsync(playerid, value)
end

game.Players.PlayerAdded:Connect(function(player)
	playerKey = "user."..player.UserId	-- user key
	print(playerKey)
	local leaderstats = Instance.new("Folder")
	leaderstats.Name = "leaderstats"
	leaderstats.Parent = player
	
	--Gold
	local gold = Instance.new("IntValue")
	gold.Name = "Gold"
	gold.Value = Golddata:GetAsync(playerKey) or 0
	gold.Parent = leaderstats

	
	--Level
	local level = Instance.new("IntValue")
	level.Value = leveldata:GetAsync(playerKey) or 1
	level.Name = "Level"
	level.Parent = leaderstats

	
	--XP
	local EXP = Instance.new("IntValue")
	EXP.Value = EXPdata:GetAsync(playerKey) or 0
	EXP.Parent = player
	EXP.Name = "Exp"
	
	--XP Needed
	local xpLevel = Instance.new("IntValue")
	xpLevel.Value = xpLeveldata:GetAsync(playerKey) or 84
	xpLevel.Name = 'ExpNeeded'
	xpLevel.Parent = player
	
	--tools
	local tools = toolsdata:GetAsync(playerKey)
	if tools then
		for i,v in pairs(tools) do
			local tool = game.ReplicatedStorage.Tools:FindFirstChild(v)
			if tool then 
				tool:Clone().Parent = player.Backpack
				tool:Clone().Parent = player.StarterGear					
			end
		end
	end




--Save data when player leaves
game.Players.PlayerRemoving:Connect(function(player) -- save player stats
	local toolsToSave = {}		
	for i,v in pairs(player.StarterGear:GetChildren()) do
		if v then
			table.insert(toolsToSave,v.Name)
		end
	end
	game:GetService("DataStoreService"):GetDataStore('Tools'):SetAsync(playerKey, toolsToSave)
	savedata('level',playerKey,player.leaderstats.Level.Value)
	savedata('EXP',playerKey,player.Exp.Value)
	savedata('xpLevel',playerKey,player.ExpNeeded.Value)
	savedata('Gold',playerKey,player.leaderstats.Gold.Value)
	print('data saved')
end)

If you guys have any tips at all i will glady accept them, thanks all!