What up PUNX ! nematodes are always worth it, you dont even need to do that foliar spray with them for them to work, which will take 14 days more or less . those rust spots though look more like text book calcium deficiency , add that in the nematode foliar spray if you do that, otherwise into the feed and the problem should stop spreading in a week and the plant will have recovered in a 14 or less even. Hope this helps ! 🚀