I’ve had those issues with my seedlings and Ilama grafts on cherimoya. It’s either intumescence or edema or a mixture. It’s a physiological response and not one caused by disease or nutrient deficiencies. Unfortunately there isn’t any definitive solutions to the problem and there are still studies to find out what causes it for other plants such as in some cultivars of tomatoes and sweet potato. In my experience I’ve had happen mostly on cloudy, gloomy and rainy weather. Edema and intumescence are different by the way but because they look similar they are sometimes used interchangeably. Intumescence is light quality specifically lack of enough ultraviolet light while edema is related to too much water uptake through the roots and the leaves aren’t able to output it fast enough and results in the blisters, high humidity and low temperatures may tie in as well. Grow lights with just the visible light spectrum do not help btw. Currently I’m testing one in a fabric pot to see if it a problem with the water uptake, but i see one spot so far on that seedling but no leaf loss as of yet. I may test it with pondapple rootstock and see if that solves it. If it doesn’t, then I may consider it a lost cause since if it is light quality then that is beyond my control. Sad because I do enjoy eating the fruit in my families country and really wanted to grow it in Texas.
Just want to add that oddly enough, it only occurs during the development of the leaf, not before when you have a tiny leaf bud, and not after the leaf has fully grown and hardened. And I manage to get those leaves to harden off when there is no overcast and rainy, or chilly weather.