Paph Magic lantern lower leaves yellowing

[Jeremy]

My Paph Magic Lantern's lower leaves are turning yellow and then soft brown, then dry brown. I decided to repot it just to be safe if there was deteriorating potting mix. However the lower leaves are still yellowing. And it seems like the yellowing is ocurring at a faster rate than growing of new leaves. It originally had 5 healthy mature leaves, but now there are only 3 healthy leaves and one leaf that is starting to yellow. The environmental conditions shouldn't be the problem since a delenatii next to it is growing fine. I give it the same amount of water and fertilizer as the delenatii. What could be the problem and how do I correct it?

Jeremy