The LEDs use 33V max, so you plan to use 36V? Seems like planned overstress to me. Something has to dissipate that extra voltage.
Pay attention on the recommendations for the unused channels also (for your future expansion).
Watch this in your PCB layout: "The exposed pad on the bottom of the package must be soldered to a ground plane. This ground should then be connected to an internal copper ground plane with thermal vias placed directly under the package to spread out the heat dissipated by the LT3496." "The exposed pad of the package is the only GND terminal of the IC and is important for thermal management of the IC. Therefore, it is crucial to achieve a good electrical and thermal contact between the exposed pad and the ground plane of the board."