Looking for info on PPM needs for larger plants in DWC

Hi All..I am on my second grow and am really hoping someone can let me know if a plants nutrients needs should be increased based on how large the plant / roots are or if they will just eat and drink more of the same PPM mix.

Basically I have same strain growing (Alaskan Ice from same mother) but one is quite large and is in a 18 gallon tote and the rest are in 5 gallon buckets...the big one appears to be a lighter green color throughout even though I have been giving them all the same strength nutrients which is the 100% recommended rate of general hydro flora series. Pretty much same feeding schedules and PH checking except that the big one drinks a lot more and is directly under the 1000 watt where as the others are under 400 watts.

I have yet to find a definitive answer on this so just been hoping it doesn't get worse but want to figure it out before it does.
My last grow of the same strain stayed very green through flower but the plant looked nothing like the one I am growing now since I didn't top the last one like I did this one.Perhaps all the larger buds require a stronger nute strength? Just don;t know.

Thank you for reading.
I will try to get pics up later but have a bunch to do before lights out...as always...lol

bigger plant can def use more food...bump it up by a couple milli litres, and watch for nute burn(tips of leaves turn brown) should darken up...

Ugh..I woke up thinking it was 8 a.m...and started getting ready for my daily to-do list...but then went outside and saw the sun was on the wrong side so looked at my phone and realized I just slept through the day...wow..lol My body must have needed it.

On the plants PPM question..I measured PH before lights went out and realized that is the one that has been dropping the PH pretty rapidly as well..I have been trying to keep it up to around 5.8 to 6.0 but within a day it drops to 5.3.

Not sure if that is why the color is not as dark but thought it may have something to do with it so will be researching that.
Still needed to know if bigger plants should go over the recommended PPM listed on nute bottles though since my hydro plants get pretty big compared to most other plants I have come across around here.

Thank you for the reply.

A drop in your pH can signify that your plants are consuming more water than nutes. To combat this, dilute your water to PPM ratio by simply reducing your nutes and add more water. What size is your res?

Thats exactly what I did before lights went out earlier this morning The res size on half of them are 18 gallons...then I am using some 5 gallon buckets only because of space limitations...what a pain having to fill up those every day.
Thanks for the reply..hoping this helps...I am writing down each days PPM and PH now..so I can see if it improves.

I am having a real hard time getting any decent photos this time round..lights and my camera are not playing well together..sigh..lol
I made a video the other day...but its kind of long and kind of embarrassed about how some of the plants look but oh well..it's only my second grow.
I also had to tear down a room...build another room plus all lights..timers..air intake etc. while the plants were in veg so they didn't get cared for that well. Then They got so big I had to just put em flower sooner than I wanted to.
Another hard to manage grow..err..lol

Anyway the plant that was looking a little pale is in at around the 3:40 mark.
This gal Looks NOTHING like my first two Alaskan Ice plants.
This one was topped since the first two I grew were done Au Naturel and got way too big.
That makes it even harder for me to know if there is a deficiency or not...sigh..lol

Oh and for anyone doing Hydro buckets that don't have big reservoirs...you may want to see what I made for filling the res up...it sure saves a lot of time compared to my old method of using small containers dipped into buckets to fill them. Look at about the 4:30 mark.