the 430 is a flowering light.
the white residue is the salts from the nutes, happens all the time. The problem you will have with a timer on a drip system, is the salt buildup will be in ur tube or like and dry out when it shuts down. then, when the system kicks on, it will add concentrated salts right away till it dillutes and remixes with your solution.

Run your system all the time. When you do a solution change, be sure to rinse out ur ring/drip tube to avoid buildup.

I use fls for veg and 1000hps for flowering and have great luck.