Tomato seedlings looking poorly

Hi, I'm growing three kinds of tomatoes... sweet pea, super sweet and basket.

The sweet pea seedlings are the smallest of the three at about two inches high. Their first/baby leaves have fallen off and it's starting to look like leaves further up the stem are weakening where they meet the main stem and are about to fall off.

On the basket seedlings, which are about four inches high, some of the top leaves are starting to curl in on themselves.

They're sitting on the kitchen windowledge in moist, not wet, compost and have tin foil behind them to maximise the light.

Any ideas?

Thanks 8doubles. Have moved them into the living room (don't have the heating on upstairs). Now sitting on a south facing windowsill with a radiator underneath them... in a tray which has been watered - fingers crossed!

Put them out in the greenhouse during the day (as long as it's not a freezing cold day)  and bring them indoors before it gets dark. They won't need the propagator, ordinary g/house temp is fine.
I've been doing this for a few weeks now and everything is growing like mad 

They are a bit leggy - pot them on individually  into some multipurpose, up to their bottom leaves and start the in and out routine, so they get maximum light during the day.
The seed leaves always drop off sooner rather than later so don't worry about them  


Don't keep them directly above a radiator it's not good for them