Debugging Health and Stamina bar?

So I am developing a Health and Stamina bar. However, I have no clue how to debug it. For my stamina bar the bar goes out of the frame. And for my health bar, when damage is taken, it does not show the players health. I also tried to make it where it shows the players headshot of their avatar. Like this

Here is my Explorer Page

Stamina script:

local CAS = game:GetService("ContextActionService")
local RE = game:GetService("ReplicatedStorage"):WaitForChild("RE")
local fill = script.Parent:WaitForChild("top"):WaitForChild("fill")

local stam = 50
local speed = 16
local sprinting = false

local function sprint(str, state, object)
    if stam < 1 then return end
    speed = state == Enum.UserInputState.Begin and 24 or 16
    sprinting = state == Enum.UserInputState.Begin
    while sprinting and stam > 0 and wait(.1) do
        stam = stam - 1
        fill:TweenSize(UDim2.new(stam/50, 0, 1, 0), "Out", "Sine", .1, true)
        RE:FireServer('sprint', {speed})
    end
    sprinting = false
    speed = 16
    RE:FireServer('sprint', {speed})
    wait(1)
    while not sprinting and stam < 50 and (wait(2)) do
        fill:TweenSize(UDim2.new(stam/50, 0, 1, 0), "Out", "Sine", .1, true)
        stam = stam + 1
    end
    while stam > 50 do stam = 50    
    end
end

CAS:BindAction("sprint", sprint, true, Enum.KeyCode.LeftShift)

Health Script:

local plr = game.Players.LocalPlayer.Character

local StarterGui = game:GetService('StarterGui')

StarterGui:SetCoreGuiEnabled(Enum.CoreGuiType.Health, false)

while true do
    script.Parent:TweenSize(UDim2.new(plr.Humanoid.Health/plr.Humanoid.MaxHealth, 0, 1, 0), Enum.EasingDirection.Out, Enum.EasingStyle.Sine, 0.1)
    wait(0.1)
end

Avatar Image Script:

script.Parent.Image = "http://www.roblox.com/Thumbs/Avatar.ashx?x=500&y=500&Format=Png&username=" ..game.Players.LocalPlayer.Name.. ""

Please help me, thank you.