i will vouch for poor water condition is probably the biggest reason to eggs being dropped.
i neglected my tank for months due to being not at home at all. started with 20 shrimp that never thrived... down to 6 shrimps.
now its rebouncing to 30 ish shrimp as im slowly trying to re-stablize the tank. Still not optimal as i still see eggs being dropped and they are definetly not new to holding eggs