[Urban Farmer]

Hello all, my tomato plant is looking rather sad today. Noticed this yellowing leaf today. Anyone know what's wrong with it? Could be magnesium deficiency?  Also, if you've had it how do you fix it? Also this is from one of the four plants I have in a grow bag on my balcony.  Little worried they may be too crowded but as they've started fruiting I think it might be too late to move them.  Thanks!

[mumofstig]

You've snapped it over the right pic - magnesium deficiency, use an Epsom salts spray as the article shows 

It's quite common

[Urban Farmer]

You've snapped it over the right pic - magnesium deficiency, use an Epsom salts spray as the article shows 

It's quite common

Thank you! Should have trusted my gut, I just thought "hmmm.. but are they yellow enough?!".