Hi guys,
I've had this philodendron verrucosum for almost a year now. This will probably be wordy, but I want to include all relevant information. I got it as a very small starter plant and it has grown quite a bit. About 6 weeks ago I chopped it in order to add a 4" moss pole, since the 1.6" one was impossible to keep evenly moist (you can see it wedged into the new one). I believed the issue I'm about to get into was due to the old moss pole being dry too often, but I'm not so sure that is the case anymore.
I've attached photos of the whole plant (photo 1), the problem leaf (photo 2), and the newest leaf that is hardening off (photo 3). The issue that I've been having since I got it, is that the moment a leaf begins hardening off, the one before it begins to get a yellow mottled pattern to it. This never happens rapidly, or even continues mottling more than what it looks like in the photo. Any ideas what could be causing this or how to fix it? It's been a bummer only having one nice leaf to show off since all the ones before it get a yellow mottled look to it.
I have it in a greenhouse, in which ~85%-90% humidity is maintained. ~74° highs inside during the day and ~69° at night roughly. I have an oscillating fan for airflow. It's been positioned 12" at the closest to the light source aimed at the plant, but is currently about 2 feet away because I wasn't sure if it was too close to the light with all the overflow lighting from other lights in the greenhouse. It's in a chunky mix I made with roughly equal parts Happy Frog soil, pumise, and orchid bark chips. I water when the pot feels lighter and keep the moss moist without flooding it. I feed with GT Foliage Focus at 3/4 strength every watering now that the cutting has rerooted and pushed a new leaf. There was a lapse in feeding when it was growing roots, so that MAY contribute to the continuation of this problem, but I'm not sure. I use insecticidal soap preventatively for pests about once a month, or when I discover pests on nearby plants. Based on all this, the most likely issue seems to be related to magnesium presence or uptake.
Any advice would be much appreciated! Bonus points if you've dealt with this issue with verrucosum firsthand. Thanks in advance!