Oh right- you have had another go
When did you sow the seed?
What happened with the seedlings after germination?
Where did you keep the seedlings once they had germinated?
When did you prick them out and pot them on?
Was it fresh seed and fresh compost?
So where did you sow them-4 plants per seed tray does not sound right-did they get any heat before germination?
Right lets start again
In about 2 months-mid -March--you need a half-tray-fill it with compost -level it- water it -let it drain
Then sprinkle the seed over the tray-cover lightly with compost seal in a plastic bag -place somewhere warm-check daily-does not need light until the seedlings are showing
Put the tray in the best lit place on a windowsill turning daily so they are not drawn towards the light in one direction.
When they are big enough-prick them out into bigger trays around 1-2 inches apart-you should get about 35 plants per tray to grow on in the cold frame-but protect from frost
They will then be sturdy plants to flower in the summer-you might want to pinch the tops out around the beginning of May to make bushier plants
Also protect from slugs/snails
Seedlings are often long and straggly when they don't have enough light. Petunias need warmth to germinate.