Answer: The lids are designed to help hold moisture in the soil while the seeds are germinating. Once they've sprouted remove the lids to promote good air circulation. If you leave the lids on, you'll encourage damping-off, a fungal disease. Adequate air circulation will help your plants avoid diseases.
It doesn't sound as though they're getting the light they require and will turn into spindly, leggy sprouts instead of sturdy little plants. Move your seeds directly under a source of artificial light, or put them on a windowsill where they can bask in the rays of the sun. In a few weeks they'll be ready for transplant into the garden!
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