Cptpwnzor's Mega Mephisto Mash-up

HELP! Just trimmed off dead and yellowed leaves about 2 days ago and peeked into the grow room this morning to find previously (relatively) green leaves starting to yellow! I admit weeks back I probably wasn't that good with Nitrogen feeding;however, now Week 7 into flowering (day 44) should I be worried or is this type of yellowing normal at this stage? Please give your advice, thanks!