budbait's first grow on growdiaries! xD

Mini spots.........looks like spider mite damage. Yellow tips is damage from hitting the soil surface at night when the leaves have been lowered down.

would like to see more of the plant. it's a mobile nute. Possibly low K ... would want to see how it progresses and any other symptoms to rule out other possibilities. seems way too early for Mg issues - those take 30-35 days to be visible AFTER the initial deficiency starts inside the plant. Is this plany a month or more old? Can rule it out if too young. the spots do look like pests suckling the leaves, but also can be early fugliness of first few sets of leaves. if that doesn't spread, not likely pests. if it's all over, inspect for pests. I think this is part of the other damage seen as opposed to pests. is their any 'honeydew' or glistening around the dots? not all will leave it behind, but that is a sign of pests (saliva or similar) the first 2-3 sets of serated leaves often have spots/blemishes that aren't related to pests or nutes. the more serious damage is something else.

I think I can see the spidermites in the 1st pic. Look under the leaf. If you see reddish brown spots that turn into stripes as you rub over them gently, those are spidermites. The yellowing I'm guessing is lack of N, you can up your dose of bio grow because all your plants are looking very pale and drop the root juice. Root juice is mostly humic acid and that is great to neutralise any pH issues you might have. It's not something you need to use tonnes of and there is a lot of humic acid in compost, so a top dress of compost or a compost tea will have the same effect as the root juice or top max.