Leaves have some yellowing

[teyger]

Can someone please help me identify what this is. Is it disease or nutrient problem? All my tomato plants in low tunnel have this on the lowest leaves, of which I have pruned off.

I will say also that these plants are growing very well and producing a lot of big fruit/good yield. Varieties are Brandywine, Mortgage lifter, Black Krim, Lillian's Yellow, Sungold. and they all have it.

[zipcode]

Magnesium deficiency. Usually caused by too much Ca/K.

[maxjohnson]

At first it seems like magnesium deficiency, but when this only happen on the lowest leaves of the plant to me it's just the plant naturally letting go of old leaves. If the overall plant is healthy, you can fertilize as much as you want, it would just put your soil out of balance.