hey there day 40 was shortly after a feeding , and actually the bat guano is very strong, so probably what happenned is something like slightly too much N which led to lockout, and yellowing on the bottom leaves which is also a symptom of N deficiency (from the lock out in your case). You can see as the plant recovered that the leaves are "really green" and a bit "shinny" those are symptoms of N toxicity (very light in your case!) so just keep doing what you're doing and avoid to much feed for ten days or more and the problem will stop spreading and not reappear. Hope this helps ! 🚀
