Your plant looks perfect! I wouldn't change a thing. When you start flowering, it's common for the lower part of the plant to start turning yellow and for some leaves to fall off. This is because the leaves at the bottom of the plant don't receive as much light as those at the top and begin to lose their function for photosynthesis. Additionally, the age of the lower leaves also contributes to them wilting and falling. But the rest of your plant has excellent color, so I don't recommend adding or removing anything you've been doing. Still, keep paying attention to these kinds of things, especially if the discoloration of the leaves starts moving up to the upper part of the plant. But as far as I'm concerned, it's totally normal, and your plant is in perfect condition. It would be normal for more leaves to fall off as it grows in its flowering stage! PS: You could check the stems to see if they have any red/purple color, which would indicate some nutrient issue. But I'm sure that's not the case!

That is usually a cal mag issue.if you aren't using something like cal mag plus or cal magic you might get some.

Hey, I recommend trimming those leaves since they generally don't get direct light. On the other hand, if you're in the first week of flowering, that's when they consume the most nitrogen energy. I advise you not to cut back on nitrogen-based fertilizers for at least two weeks during flowering; this really helps with proper and successful stretching. Hope this helps!