So, I switched from half-strength Lucas to full strength in preparation for the flip.
Immediately my new growth went from dark green to very light green.
At half-strength your plants were dark green. This is an indication of too much nutrient for the amount of light.
You doubled the strength without increasing the light on already over-fed plants. The leaves are lightening because they're about to yellow, crisp, turn brown and fall off. They're frying....
Keep it at the half strength or even a bit less, especially before flowering... anything to keep from going dark green at any time. Always better to under-feed a bit than any amount of overfeeding.
Stay Safe!