Why is my script complaining a gui is not part of PlayerGui?

I have this script and when there are multiple people in my game I get the error saying that "playercheckgui9" is not a valid member of PlayerGui

local repStorage = game:GetService("ReplicatedStorage")
local event = repStorage:WaitForChild("BossDied") 

game.Players.PlayerAdded:connect(function(plr)
	local client = game.Players.LocalPlayer
    plr.CharacterAdded:connect(function(chr)
        chr:WaitForChild("Humanoid").Died:connect(function()
			print('Boss Died')
         	if plr.TeamColor == BrickColor.new("Bright red") then
				for i, v in pairs(game.Players:GetChildren()) do
					local guis = v.PlayerGui:GetChildren()
					   for _, v in pairs(guis) do
   					         if v.Name == "Shop" or v.Name == "TouchGui" then
						else
						v:Destroy()   	
    					end
					end	
				end	
				for i, v in pairs(game.Players:GetChildren()) do
					if v.TeamColor == BrickColor.new('Bright red') then
						v.TeamColor = BrickColor.new("Bright yellow")
					end
					v.Character.Humanoid:UnequipTools()
					if v.Character.Humanoid ~= nil then
						v.Character:BreakJoints()
					end
				end	
				for i, v in pairs(game.Players:GetChildren()) do	
					local player = v:FindFirstChild("PlayerGui")
					local screengui9 = Instance.new('ScreenGui', player) 
					screengui9.Name = "playercheckgui9"
					-- Create textLabel
					local textLabel9 = Instance.new('TextLabel', player.playercheckgui9)
					textLabel9.Position = UDim2.new(0.45, 0, 0.4, 0)
					textLabel9.Size = UDim2.new(0, 250, 0, 100)
					textLabel9.FontSize = "Size28"
					textLabel9.BackgroundTransparency = "1"
					textLabel9.TextStrokeTransparency = "0"	
					textLabel9.Text = ("Round Over")
				end		
				for i=1, 50 do  
					for i, v in pairs(game.Players:GetChildren()) do
						local label = v.PlayerGui.playercheckgui9.TextLabel
						label.TextColor3 = Color3.new(math.random(), math.random(), math.random())
					end
					wait(0.1)
				end
		wait(5)
				for i, v in pairs(game.Players:GetChildren()) do
   				local playergui = v:FindFirstChild("PlayerGui")
  					if playergui then
   		 			local somegui = playergui:FindFirstChild("playercheckgui9")
    					if somegui then
    						somegui:Destroy()
							print("Destroyed ninth GUI in PlayerGui")
						end
					end
				end	
			end 
        end)
    end)
end)

Your using a local script (As shown by local client = game.Players.LocalPlayer). However later on you try to make a change to other players. You should use a server script however it will require a change to your script.