30 days in rusty looking leaves

Towards the beginning of the grow I had yellowing of inner leaves I'm using a smaller tent only a 1x5 I'm considering moving my plants outside I'm currently using a 300w CFL running them with canna Coco part a and B, I will be upgrading to a larger tent I'm open to any suggestions I'm a new grower not a lot of experience the larger plant is an Autoflower white LSD they were both planted on 07/10/20

Im unsure why it looks rusty I'm not an experienced grower this is only my second grow any tips will be appreciated I would love to get an idea how to treat it