I'm wondering if anyone can tell me what's going on with my cassias?
The leaves are deformed, with no evidence of pests. The puzzling thing is not all the leaves are deformed. (see pics). The bottoms of the leaves have small hooks on them (see circles on pic). I started noticing this this past winter (2013-2014). At first I thought they may have had some problem from the extended cool weather we had.

Some background information:
We do not use any pesticides on our property.
I'm in SW Florida (Cape Coral) and have numerous cassias in large clay pots hooked up to a drip irrigation system. This system uses reclaimed sewer water that our city provides. The system is on timers and they get watered consistently.
The cassias have been growing in the pots for YEARS here, and I have never seen the cassias looking this way before.
There are also a few growing in the ground that are experiencing the same thing.
Any clues? Thanks in advance!