Sickly tomatoes

[annie8]

My sister has a couple of tomatoes that are looking sickly. Looks to me like a deficiency- magnesium? She has been feeding it with seaweed feed, not sure if that is the cause, maybe switch to tomato feed? It is just those two, the other ones she has are fine.

[ameno]

I don't know if it's necessarily magnesium, but it's definitely a deficiency of some sort.
Also, seaweed extract is actually pretty low-nutrient. It's recommended as a plant tonic or as an additive to other feeds, not as a plant fertiliser in its own right. On its own, it just isn't nutrient-rich enough to use as a liquid feed.