Trimming Fan Leaves in Flower

defol is very useful but as you're 3 weeks + in flower , they won't replace rhenneded ones only recover the same. ideally no later than day 21 in flower for a defol. removing the odd leaf that is blocking light won't be an issue really. try tucking it behind something or moving it 1st , if not pull out. The lower bigger fans become blocks for airflow too which is really important to keep good as the buds thicken. getting air around them is vital too. you won't damage with defol, if anything and worse case , you would stunt the growth . dont worry , these are hardy plants that survived for millenia in some harsh conditions too.