Plant Wilting Randomly (Need Input Please)

So the other day I looked in my grow closet and it was around 9:15 pm and one of my plants had wilted. Earlier that morning I had watered my plants and left for the day as I would any other day and both were in great health and had no signs of problems. I have 2 plants in this closet that were ready for flowering and I began to flower about 2 weeks before this wilting incident had happened. During those 2 weeks I havent had any problems with my girls until I saw it had wilted one night. I switched my lighting from 12/12 to 20/4 again to bring my plant back to life and let the dead leaves I cut off heal and now a week later the one plant is back to normal. But now my other female did the same thing 2 days ago. I still have my lighting on 20/4 to help the 1 but now the other did the same thing. Does anyone have any thoughts on what might of went wrong or what the cause of this was? Any input is much appreciated.

My setup:
x2 2ft T5 Veg Bulbs
x5 23w CFL's (Daylight)
-Mylar surrounds the entire closet
-x2 female plants
-30in X 34in X 8ft (closet)

Do you have a decent source of fresh air getting to them at all times??

Pictures would be really helpful in diagnosing their problem!
It sounds like a over/under watering issue, but without a photo it's hard to say...
also Changing their light schedule from 12/12 to 20/4 is regressing from flower to veg thus stressing your girls. This type of stress can lead to hermaphrodites, and other growth issues. Next time I would recommend staying in 12/12 and only taking foliage that is 50% damaged or more.
Hope this helps!
MR