I took my tomato and pepper seedlings on holiday with me (doesn't everyone?), and they grew a staggering amount in a warm boiler-room. Thing is, they were on a window sill in their shallow starter soil and were not fed. The result is tall, leggy and rather puny plants, with the lower leaves going a bit yellow/red.
My instinct is to repot in deeper soil, pinch out the tops and feed with liquid tomato feed.
Is this right? Do you have any other suggestions, please?