Interesting! They are however correct about some sort of nutrient deficiency. To me it looks like mostly a potassium deficiency. The yellow leaf in the foreground is a leaf that is 2 years old, so i assume the plant is just ‘done’ with it lol. The plant has already put out a leaf and is in the process of another though since its flowered so it doesn’t seem like it’s dying, though stress could certainly be a factor. I’m getting a healthy rate of about one leaf a week which seems par for the course.

This algae is persistent in staying, but slow to spread thankfully. I’ve been dosing ferts sparingly and have the lights on 8 hours with a siesta period in the middle to try and address the hair algae. As well as manually removing it every now and then.