what's the problem

When i turn on the light the leaves lose the strength I’m giving the. 18/6 light But don’t know what the problem could be Please help

Okay I have 2 plants I've grown from seedlings they're about 3 feet tall but one of them is flowering the other isn't it's clear they're 2 different plants I feed and water them at the same time but the one that's not flowering is purple from root halfway up the tree but but appears to be very...