Previous bought sword duplicates? (Dev Product)

I am making a sword fighting game and I made a dev product shop (for swords, powerups, etc.) There's a glitch where the previously bought sword duplicates when buying another sword. Here's a small part of the code, it's just for one sword. NOTE: This isn't the full script!

if purchaseInfo.ProductId == 1016546798  then
          local sword = game.ServerStorage.Swords.Darkheart
        local swordClone = sword:Clone()
        local swordClone2 = sword:Clone()
        swordClone.Parent = plr.Backpack
        swordClone2.Parent = plr.StarterGear

Note: The sword is only meant to be usable in a single server. The gamepass part is already done. Here's a video of the bug: https://www.youtube.com/watch?v=FPsKXGAuWhs&feature=youtu.be

EDIT: Here's the full script:

local marketPlace  = game:getService("MarketplaceService")

marketPlace.ProcessReceipt = function(purchaseInfo)
        local plr = game:getService("Players"):GetPlayerByUserId(purchaseInfo.PlayerId)
    if purchaseInfo.ProductId == 1016546798  then
          local sword = game.ServerStorage.Swords.Darkheart
        local swordClone = sword:Clone()
        local swordClone2 = sword:Clone()
        swordClone.Parent = plr.Backpack
        swordClone2.Parent = plr.StarterGear

        elseif purchaseInfo.ProductId == 1016545986  then
          local sword = game.ServerStorage.Swords:FindFirstChild("Illumina")
        local swordClone = sword:Clone()
        local swordClone2 = sword:Clone()
        swordClone.Parent = plr.Backpack
        swordClone2.Parent = plr.StarterGear
        elseif purchaseInfo.ProductId == 1016548359  then
             local sword = game.ServerStorage.Swords.Firebrand
        local swordClone = sword:Clone()
        local swordClone2 = sword:Clone()
        swordClone.Parent = plr.Backpack
        swordClone2.Parent = plr.StarterGear
        elseif purchaseInfo.ProductId == 1016547469  then
           local sword = game.ServerStorage.Swords.Venomshank
        local swordClone = sword:Clone()
        local swordClone2 = sword:Clone()
        swordClone.Parent = plr.Backpack
        swordClone2.Parent = plr.StarterGear
        elseif purchaseInfo.ProductId == 1016549468  then
             local sword = game.ServerStorage.Swords.Icedagger
        local swordClone = sword:Clone()
        local swordClone2 = sword:Clone()
        swordClone.Parent = plr.Backpack
        swordClone2.Parent = plr.StarterGear
        elseif purchaseInfo.ProductId == 1016548880  then
            local sword = game.ServerStorage.Swords.Ghostwalker
        local swordClone = sword:Clone()
        local swordClone2 = sword:Clone()
        swordClone.Parent = plr.Backpack
        swordClone2.Parent = plr.StarterGear
        elseif purchaseInfo.ProductId == 1016547105  then
           local sword = game.ServerStorage.Swords.Windforce
        local swordClone = sword:Clone()
        local swordClone2 = sword:Clone()
        swordClone.Parent = plr.Backpack
        swordClone2.Parent = plr.StarterGear
        end

    end
    return Enum.ProductPurchaseDecision.PurchaseGranted