TOMATOES HAVE STOPPED GROWING

Took some kitchen roll tubes and cut these into three. Then each mini tube was filled with seed compost and I planted one tomato seed in each - 20-odd altogether, Shirley and Gardener's Delight. Pretty much 100% germination, but they seem to have ground to a halt as seedlings. Don't seem to have grown much at all over the past week or two.

I keep the compost moist but not soggy. Don't water every day. They're in the greenhouse as I don't want them to get leggy, but could it still be too cold in there? No heat as such, only a tiny heater to keep it frost free. Obviously lovely when the sun shines, but perhaps they don't like the fluctuations in temperature? Ranges from about 5°C some nights to 25°C+ during the day.

Any thoughts?

Mangetout planted in the same way are romping away, except used growbag-type compost.

Yes I think perhaps you're right. Received wisdom is that they should be in 3" pots by now.