m0useanswered grow question 3 years ago Your plants being stressed somehow and this is a result of it.
Normally this stress is heat related I find. It can also be from soil issues as well ranging from roots to PH and the odd-time light stress, to bright or not bright enough.
Find the stresser and help them relax.
you cant fix the ones that have done it already but maybe they will thicken up.
also read some times a plant can be predisposed to fox trailing traits more then others.
Good Luck