Cilantro just got checked.
This looks most like etiolation: the cilantro is stretching for light, so the stems stay thin, long, and unable to hold the leaves upright. In the photo the plant is alive and green, but the growth is sparse and lanky rather than compact. That matches your note that cilantro and parsley are growing skinny and falling over. In a hydro setup like this, weak light is the most common cause; low airflow can make the stems even floppier.
What to do today
Improve light and support the seedlings before adding anything else.
Also possible, but less likely
What would prove it
Watch for tighter, stronger new growth
If light is the issue, new leaves should emerge closer together with shorter internodes and firmer stems. If the plant keeps stretching despite better light, check roots and feeding next.
Turn this into a recovery case
One photo gives a diagnosis. Tracking proves whether the plant is recovering.
Don’t leave the diagnosis hanging 🌱
Save it now, then use the next photo to confirm if this was the right call.
Create account & save plant 🌱