locking up

so locking up is when salts build up in the soil, right? how can you tell when your plant is "locking up"? what are some symptoms?

Ive heard and read that a pale green plant is a good indicator of "lock-up". I can honestly say that im not 100% though!!

a sickly pale green that is =D.....

I got this little passage out of my grow bible by G. Green.

CAUSE:
Lockout occurs when the plant cannot access a nutrient or a group of nutrients. This could be caused by the absence of nutrients ( a deficiency) or by a chemical reaction in the medium/solution, which either causes a toxic substance that changes the chemical properties of the other nutrients...

pH problems can lockout nutrients. The wrong soil type can also cause nutrient lockout. Out of date liquid feeding products can precipitate, causing nutrient lockout. Salt is another compoint that can cause nutrient lockout.

SOLUTION:

Lockout can only be solved by flushing or transplanting and with hydroponics you will have to change your nutrients

Just to add something to that... It's good to invest in something like Flora-kleen or another flushing solution, they are cheap and help a lot. Whenever I have a nutrient issue I always flush with that and then soak with a complete, but rather dilute fertilizer, to make sure they still have enough nutrients to keep going. Superthrive ill help a lot as well, keeps the plants from being stressed from the flushing and helps maintain growth.