Hi , It looks like a fungus /rot problem , I would give them a good going over with some Daconil might not be spelled right , can get it at one of the large stores that have plant sprays ect . If any of the spots are soft and seep , section them out of the leaf , apply the spray and coat the cuts with cinnamon , keep the damage dry , and be sure they have good air circulation . If they have had a bug problem sometimes the trouble is secondary . Good luck with them . Gin