your ppms may be a little high... but that plant looks mighty nice in the picture.
i know there are strains that will take 1200+ ppms.
i also know that ph drift is important to the uptake of nutes.
on the other hand, and it may seem contradictory, you don't want drastic ph changes... slow & gradual is the key.
the idea is : as the plants takes in nutes & water, the chemistry in the bucket changes.
at lower ph or higher ph, plants will uptake certain elements... and this is where "lock out" comes into play... the plant(s) wants/needs an element but the ph is not in the correct range for that element's uptake.
i have been experimenting with ppms quite a bit in a extra bubble cloner i have ...& what ppm to run depends on factors like: strain, plant & stage (seed, early veg, early flower, flower), clone, environmental conditions, etc...
i never rock seedlings in dwc; so, that's a moot point there.
i only go from clone to dwc; this way, i can be absolutely sure i've got good, long, hairy roots that go right down into the bucket.
i run clones at 200 to 350 ppm
i run veg at 350 to 600
i run early flower at 600 to 750
i flower at 750 to 1000+
still, like a good pimp, i let my ladies tell me what they need.
i study up all the time in the "infirmary section"... i check pics of people issues, read (and re-read) the stickys, and study my own plants.
change outs : i know dudes that NEVER change their buckets & do great... just as i know dudes getting root rot on the regular.
prevention is the key. being clean is the key. disolved oxygen (air pump) is the key.
yes, i change out every 7 days if i am feelin spry... 10 days if i am feeling lazy.
i also change out often because i could care less what my water temps are.
be careful with frozen bottles, roots will die when left exposed to ice cold bottles for long times.
just use the right size container scaled to your bucket.
i was thinking of maybe going to igloo coolers (genius), like bloomer57, but right now it's just an expense i dont need.
insulating the buckets is cheap & easy.
however i change out on the regular and use the nute water on my lawn & plants.
i run 6 buckets & keep 6 extra buckets & lids all clean & ready to go with extra tubing, extra stones, and all that.
so, every week (+ or -) i start fresh.
until i go rdwc & buy a chiller, my low maintenance dream, i just change out on the regular.
hygrozyme (or cannazyme or multizyme) and h202 are your best friends... just know when to use each & never over do it.
depending how far into my change out schedule, i don't always add nutes to the buckets. when i do change out : i get my water level right, mix my nutes & double check ppms, & THEN set my ph.
if i am feelin nerdy, i do the water & nutes the day before... and adjust ph the following day. i don't check ppms everyday unless the plant is drinking tons of water... which will change bucket chemistry.
with a ppm meter, you can actually see when the plant is taking nutes out of the solution.
with your eyes, you can see when the plant is "drinking" water.
you just adjust accordingly.
i do keep 3 gallons of pre-mixed, NON PH ADJUSTED, nutes (for whatever stage i am in) at the ready in case i need to top off.
i simply break off a gallon into a container & adjust the ph right before i add to a bucket(s).
with three closets going, a cloner, my experiments, and cracking beans, i do spend at least an hour every day in my garden... so i always know what's going on.
don't think for a second that root rot will not happen. when it does happen, it jumps off fast.
i don't adovcate not checking/controling your water temps.
i just don't play that (and another) game.
with ph, i think, most hydro guys like to start in the 5's with ph.
as i said, i like 5.5 (ish).
i DONT play the ph game either... i let it drift & adjust if i need to.
did i answer all your questions?
if not, flo grow, has his shit quite tight.
he's an excellent source of information.
and, i will check back.