Hi Sorry to hear it is Marek's but definitely better to know and taking the steps you have already taken and plan to take will help limit the effect on your flock. I like that you are planning more run space for them for winter. Cutting back on high carbohydrate treats like scratch, corn or bread is a good idea. Providing them with access to fresh greens and surplus fruit whenever possible is a good idea and as Wyorp Rock suggests a vitamin supplement once a fortnight would not be a bad idea. As regards wormers, I'm of the opinion that you don't want to be pumping chemicals into their bodies if they don't need them as that can stress their internal system. Was there any mention of internal or external parasites on the necropsy report. If this is your first flock and chickens have nor recently been kept on the same ground, then they may not be at risk of a high worm burden at this stage. Rather than routinely worm, you might want to send off a combined flock sample to the same lab as did the necropsy, for a faecal float test. That will give you an indication of whether your flock have a worm or coccidia load that needs treating..... Marek's can cause secondary infections like coccidiosis overload, due to the immune suppressive nature of the virus. The faecal float will not usually identify tapeworms though so you need to be vigilant when you are cleaning up poop for tapeworm segments. Tapeworms are less common than roundworms or cecal worms but it is importand to know what you are looking for..... ie tiny white or cream coloured organisms like grains of rice that move slowly. If you research tapeworms in chicken poop I'm sure you will find videos of what to look for. Some climates will lend themselves more to worms than others. In 5 years of keeping chickens I have yet to worm my flocks. I have seen the odd roundworm in poop and found a couple during necropsies (maybe 5 in total in 5 years), but it is my belief that a low level of worms is to be expected and it is only when their system gets out of balance that an infestation gets out of hand. Many people disagree with me and routinely worm their flock and feel than any level or internal parasites is not to be tolerated and will always result in an infestation if not treated and that may be the case in some climates, but my preference is to be vigilant and have poop samples tested once or twice a year and only treat if necessary..... I operate the same system for my horses and have found from the results that routine worming is not necessary for me. You will need to make up your own mind as to which route you want to take. Something that I think can be beneficial with chickens in general but Marek's flocks in particular, is fermented feed. It is easy to do and provides them with more easily digestible food and keeps their gut bacteria healthy. I'm also a fan of a little raw apple cider vinegar in their water. I also think that deep litter floors, in the run at least, provide them with a healthier environment. Other than that, it is just a question of playing the waiting game to see if/when you have another outbreak. Good luck!