Thanks everyone for your replies! Sorry for the late reply, haven't had the chance to visit the forum lately.
Unfortunately, the previous batch of seedlings didn't make it.

But the good news is that we found another way to make it work! We've planted our basil and coriander seeds in styrofoam boxes with cling wrap that we poked holes in for ventilation and water, and left them out in the garden. Worked a treat! They're still small but at least they survived long enough to grow their true leaves. Fingers crossed now!