It doesn't look very happy. I wonder if it could be herbicide damage.

Linda

What has he been spraying them with? I see some residue on the leaves.

Linda

Is it only on the new growth?

Just from the one photo, it looks a lot like damage caused by psyllid feeding, which can cause stunted/curly leaves and yellowing with purple veins. Any sign of sap-sucking pests on the plants? Could that white residue be their honeydew/poop?

But it could also be nutritional (especially if nighttime temps have been cold lately where your grandfather is, as cold temps interfere with uptake of certain things) or herbicide related as Linda says. Or a virus.

Just found out that if that is psyllid yellows, the pest and the disease need to be reported in Australia, as it's a new pest/disease to the continent.

Nope, my grandfather never uses herbicides in any part of the garden, including lawn. The stuff on the leaves is tomato dust which is a mix of spinetoram, copper oxychloride and sulphur.

I didnt see any signs of pests, no honeydew... does psyillid yellows cause flowers to form on the tips of shoots?

The summer here has been a bit all over the place. Weve had quite a few unusually cool days where the max temp has bee about 20 degrees celcius followed by days of 30+. Maybe a genetic disorder?? Since its just two plants that are affected. I told him not to save the seeds from those plants

And yes its just on new growth, by observation it seems to have grown like that and not slowly developed it. If that makes any sense

If you're not seeing actual psyllid nymphs or eggs, then it's unlikely, which is good news.

Herbicide can come into a garden in mulch, compost, and manure from an external source. It can also drift in from a neighboring property. However, that damage doesn't look typical of herbicide damage to me. Doesn't mean it can't be, though.

I'm leaning toward nutritional.

No signs of any problems on older foliage? No discoloration or marks there? If this is limited to newer foliage right now, my first guess is sulfur deficiency.

Nothing on the older folage at all. It's very healthy. The leaves are completely green with no signs of chlorosis. He originally ammended his soil at the beginning of the season with homemade compost and has been feeding the plants with blood and bone with an npk of 5.5:4:3.

It would be weird for sulfur deficiency to happen in soils amended well with compost. You could always get a soil test (a soil test is never a waste of time, but get it done by a lab. The home test kits are not accurate at all. The Dept. of Industry should offer soil tests.) It's not nitrogen deficiency, which would show first on the oldest foliage. Phosphorus deficiency, which happens frequently in cold soils, is usually a dark purple overlay, not that bright purple over pale leaves, and your temps don't seem to have been all that cold.

After looking again at the buds in the first photo, I wonder whether what we're seeing is the early symptoms of big bud disease, which is a phytoplasma.

Check out the following and let me know whether anything there is sounding familiar. Once some of those buds start to open, you should know for sure.

Text descrption of tomato big bud: http://www.plantwise.org/KnowledgeBank/Uploads/PestNet/Tomato_big_bud_(212).htm

Illustration of big bud from NSW Dept. of Industry:

And here's a page you might find helpful: https://www.researchgate.net/post/Does_this_tomato_plant_have_a_viral_infection

I could be overthinking this, though. Maybe someone else will come up with a more obvious explanation.