A large amount of moisture is gathered in the masks during the treatment, which is then coming out the top of the mask, on to the lashes. Moisture cures the eyelash extension adhesive, so therefore the adhesive is curing a lot faster than you are used to, and therefore not being properly attached. 
 
A few recommendations we have to resolve this are:

Use Disposable Masks
Change clients masks to a disposable mask before the treatment, we find these are a lot easier to tape down, reducing moisture coming out the top.

Transpore Tape
Tape top of mask down with Transpore Tape, as this is a stickier tape, we find it works better.

Master Artist Adhesive
Switch to our Master Artist Adhesive, if not already using. This glue works in a wider humidity range, and therefor would be more suitable for the additional moisture, and not affect the setting times.

Reduce The Temperature In Your Room
Have a cooler room, not the most suitable tip as its getting colder outside, but this will speed down the setting time of the glue, to counteract the additional moisture.

Ask Clients To Keep Talking To A Minimum
Ask the clients not to talk, this creates even more moisture, and means the masks will be moving, releasing moisture.

Use A Humidifier
Buy a humidifier, to keep a constant check on the humidity and temperature in the room using a hygrometer.