Little watering, I would increase it to at least 250ml, the soil looks a bit dry, do you stick your finger in to check if it's moist? What temperature and humidity do you have? With airpots, you won't have overwatering issues unless you give them too much.
Try to maintain the following conditions: 22Âș - 26Âș Celsius, 60% relative humidity.
Increase the watering to double and spread it well, keep checking the soil, don't let it dry out completely.