you definitely should remove the tin foil, it is absolutely horrible for your plants. If your thinking of using mylar... maybe you should stick to white walls, they are about 80% reflective to light and mylar is very hard to work with, it dulls fast and keeping it clean is pretty much impossible. Im currently using 2m mylar and wish I would have saved myself the money and gone with white walls. You should also keep the oscillating fan in there at all times, it's good for the plant to sway back and forth... thats how you make it stronger.
Mainly I would just recommend that you work on the ventilation, your babies look heat stressed. Good luck bro :]