How do you deal with young corianders which wilt after watering?

I'm from Malaysia, on the equator, about 37-39 Celsius, sunny and rainy all year around. After about 1-2 weeks, growing coriander from seeds in an outdoor yard, covered with a semi-transparent polycarbonate - shady but let's through sun - I find that they suddenly grow, but these young ones very easily wilt when I water them, even with a light shower spray. Please help!