Magnesium deficiency tomatoes

[Beil]

Lower leaves are getting blotchy yellow and eventually dying.
I'm 'thinking' magnesium issue and it's being transported to to the newer growth as it's only the very lowest leaves affected, up top they look healthy AF.
I don't believe I added any additional Mg to the soil mix originally.. will double check, but pretty sure it was just Coco coir, perlite, loam/sand, manure, richgro organic blood bone- tomatoes, gypsum, shell grit, kelp meal, guano.
Possibility of potash, can't remember if I had any left ...

 

[Harry bootlace]

I can rarely grow tomato’s.
Dont know why. .

 

[Pixie]

I think you can spray them with bi carb

 

[benn0]

looks like you've got plenty of new growth there mate so I wouldnt be worried unless more leaves start turning. could be the lower leaves are dieing off from lack of sunlight, when I twine my tomatoes I often pluck off all the lower leaves only leaving the trellis of tomatoes left.
if your worried you can pick up some magnesium sulphate from bunnings, manutech i think is the brand and give the roots a treatment, its often advised for backyard growers as its fairly common occurance