You may want to shift this topic to somewhere like Game Design Support instead!
I’m not so sure if this is a memory leak, as this may just be caused with how Roblox allocates the memory, considering the different OSs used. This may also be caused by other programmes running outside of Roblox, and thus having lesser memory to run the game on
If you still want to ensure that your game isn’t experiencing some sort of memory leak, you can refer to this post, which pretty much summaries how to handle these leaks pretty neatly: