I just grow in the cooler. A marine cooler has a 5 day ice rating, maintains temps on it's own. Adding a few extra air stones will also help with temps.
Trimming the crap out of the plant is what I do in those situations. Cutting at the closest nod to the stalk and of course topping it as far down as possible. The more it boots for regrowth the more it thickens up. Problem is it set's veg time back by weeks and will leave you with insane roots...
From lockout of from to low of a dosage, either way it looks to be cal/mag deficient.
The safest rout to see if it is locked out is to change rez to straight water. If it drinks up right away it's a straight up deficiency, if it takes a few days to drink normal it was locked out.
If it...
Guessing a calcium def.
We would drain the rez and fill it with straight water and give it a day to see if it's drinking. Once it starts drinking we reintroduce nutes to the system. Ph adjustment may be needed if the problem returns.
If it drinks right away it's in need of more cal/mag, if...
My rez climbs up close to 7 by the next top off while using our Flushing agent, but we take it back down to 6.
Some products require different ph levels, so you might what to check the bottle for a suggested level. My line calls for 5.8 to 6.0 yet others suggest low 5's.
Yeah, this looking at a pic and reading a few sentences isn't exactly the best way to figure some of these things out.
Nutes, dosage, water temps, ph levels, stain, man the list of factors can go on and on.
The plant does not starve, it feeds off the reserves the plant naturally stores in the leaves and stalks, this includes burning off of any residuals left by the chemicals we use especially bloom boosters.
A good read for anyone that's interested in more information on Flushing...