I am growing 14 tomato plants in 30 gallon fabric containers and one of my plants, a Mortgage Lifter, started developing a yellowing pattern that I haven't seen before. Its sort of mottled with yellow uneven patches. At first I thought this may be a magnesium deficiency, but it's not looking like it. I'm am growing in new potting mix (Fox Farm Happy Frog potting mix) and have been feeding it with a small handful of Happy Frog granular fertilizer every 2 weeks. I water by hand approximately every 3 days with a hose at the base. Checking moisture levels regularly so not to dry and not too wet. Spray every 2 weeks with bonide copper fungacide. Any thoughts as to what this could be. Its only affecting one plant out of 14.

Thanks all!!