you're at 3-4 weeks, they need food. you also have 3 alternating internodes, which is another indicator to feed. the cotyledons (water leaves) aren't a good indicator of when to feed. i've had mine stay on for quite some time. clear cups aren't that big of a deal, but you def should have holes in the bottom for drainage. i would also suggest staying away from vermiculite. in soil, the last thing you need is something keeping it wet longer. you actually want it to dry up between waterings/feedings.