Help, pests in flower how to identify and treat

Doesn't look like pest damage to me either. Could be nutrient issue. It can also happen if the plants have been indoor or in soft light and then go in the sun on a warm day. If they're not hardened off they can burn easily.

Ca deficiency

I wouldn't say it was through a pest either. There is possibly something off with your nutrition uptake. Next watering test the PH of your runoff. If that's way out of range you may have a lockout.

I agree with mOuse, it looks more like a serious problem. Have you checked your runoff for pH and thus nutrient uptake? The pH should be between 5.8 and 6.5, and you should also check the EC value; it shouldn't be over 2. Spider mites and fungus gnats/beetles look different. With spider mites, the plant is covered with small white threads like spider webs. With fungus gnats, there are usually white elongated spots where they pierce the leaf, like tunnels. So I don't think it's from insects. I haven't seen any such damage from them so far.

Looks like classic leaf miner damage to me. The trails and blotchy necrotic spots between the veins are a giveaway. The eggs under the scope could be leaf miner larvae or eggs, as they lay them inside or just under the leaf surface. The best course of action is to remove the affected leaves to prevent the spread, and consider treating the rest of the plant with a product like spinosad or neem oil. Keep an eye out for any new trails or flying adults.