Tower defense Tower targeting and attacking. Anyone got answers?

I think its about time i asked the community for help. I've searched the dev forum and everywhere for answers, and have found none.

So as the title suggests, I need help with my towers. I have a somewhat accurate targeting system, and the script just errors when i made it kill enemies. Right now, when the enemy get out of range, it doesn't always switch to the first enemy. Currently my targeting system uses something I found on the devforum. Basically, each enemy has a Pos Value which increases depending on the speed. The tower then finds the one with the highest value in its range, and then sets it to the target. I'm not sure why it isn't working, so any help is appreciated. The problems with the attacking is when the enemy is destroyed, the script can't find a target and completely errors.

Here is the targeting script:

Turret = script.Parent
Range = Turret.RangeBubble
EnemyFolder = game.Workspace.Enemies
debounce = false
local CurrentTarget
while true do
    local enemies = game.Workspace.Enemies:GetChildren()
        wait(0.001)
    for i, Enemy in pairs (enemies) do
        if Enemy:IsDescendantOf(game.Workspace.Enemies) == true then
            if (Turret.BulletStart.Position - Enemy.HumanoidRootPart.Position).magnitude < Turret.Configuration.Range.Value  then
                PositionNumber = Enemy.PositionNumber
                BeingTargetted = Enemy.BeingTargetted.Value
                if CurrentTarget == nil or PositionNumber.Value > CurrentTarget.PositionNumber.Value then
                    if (Turret.BulletStart.Position - Enemy.HumanoidRootPart.Position).magnitude < Turret.Configuration.Range.Value then

                            CurrentTarget = Enemy

                    end
                end
                if (Turret.BulletStart.Position - CurrentTarget.HumanoidRootPart.Position).magnitude > Turret.Configuration.Range.Value then
                    CurrentTarget = nil
                end
                Enemy.BeingTargetted.Value = true
                Turret.Targetting.Value = CurrentTarget
            end
        end
    end
end

The attacking script(without the damage):

Turret = script.Parent

while true do
    Targetting = Turret.Targetting
    Snake = Targetting.Value
    wait(0.01)
    if Snake ~= nil then
        HRP = Snake.HumanoidRootPart
        Beam = Instance.new("Part",workspace)
        Beam.Size = Vector3.new(0.5,0.5,(Turret.BulletStart.Position - HRP.Position).Magnitude)
        Beam.CFrame = Turret.BulletStart.CFrame:Lerp(HRP.CFrame, 0.5)
        Beam.CFrame = CFrame.new(Beam.Position, HRP.Position)
        Beam.Anchored = true
        Beam.CanCollide = false
        Beam.BrickColor = BrickColor.new("Bright yellow")
        wait(0.01)
        Beam:Destroy()
        Turret.TurningPart.CFrame = CFrame.new(Turret.TurningPart.Position, HRP.Position)
    end
end

Note that my enemies use humanoids. This is something i don't want or plan to change. I would prefer not changing it.