[Arid_gardener] Cotton Wood loosing leaves

[L V]

I have 2 cotton wood trees, one 6 yrs and the other 2 yrs old and they will 
all of a sudden loose a ton of leaves and they look really bare.  I slow 
drip water them once a week for about 8 hours and also water on a faster 
drip 1 other time during the week.  I know they need a lot of water, but it 
seems to happen after I have watered them.  They look really unhealthy.  Any 
ideas what I am doing wrong?

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