Why are they in such small pots? Are you growing plugs for sale?

Are they from seeds or runners? First year plants should be allowed to grow roots and develop plant and pinch off flowers, so no fruit.

Such small pots look like not enough water or soil to get nutrients from to grow or fruit anyway. How are the ones outside planted? They look nice and green so I dont think its light, but loss of water thru transpiration can make leaves droop or curl to conserve moisture in plant.

My strawberries have long roots that spread out in ground or containers, but containers are wide to let crowns grow and spread. A strawberry planter has open top and holes on side for plants or runners to root in, but if you transplant you find roots have grown through out planter top to bottom and can be a foot long.

Thank you very much for help. The seedlings are from runners. I put the seedlings in pot because I want put them in to cold house to break dormancy and have fruit earlier.

The pot is not too small, 10cm*10cm，I only put the seedlings into the pot for 1 weeks in the cold house, and totally stay in pot for 1 month,then transplant , so I think the pot is OK, other pot seedlings stay in outside is growing well, I set them as CK.

And the water is enough,I check everyday, and add water for the dry one. I keep the RH 70%-90% in the room.

The cold house is about 22 square metres,but only 10 fluorescent lamps(36W), and the distance between the plants and lights is about 1 meter. The under leaves are thinner and softer , and edges are darking ,water-soaking and curl . The new leaves are yellow color. So I think maybe the light is insufficient, and maybe below the light compensation point. I do not have a LUX tester. one week's weak light maybe make them hunger.

What variety of strawberries? some are for northern and some are for southern which means they can take different cold temps in winter/dormancy and different heat levels during growing. Some varieties do well in high humidity and some suffer.

Next you have to look at what nutrients do you feed? A general fertilizer or specific for fruit? Many berries like more acid in soil or fertilizer to absorb what they need from soil. Sometimes yellowing leaves is chlorosis and you need iron or other adjustment to soil or fertilizer. Check for insects as well.

Thank you for your suggestions, I will check.