Pests bites from leaves?

Your using a heavy dose for such a young plant. How many times are you feeding? Just once a wk right? Looks like she's a little over fed, and leaf damage can happen by moving pots around, pinching a leaf. I think you'd notice a catherpillar or even such a large bug would eat that much in 1 sitting. And if it were any lil things, youd have multiple very small sites with damage, holes, and you can tell nute marks, on healthy leaves more often than not if you have a mag you'll be able to see where they were eating. Anyways just looks like a simple tear. But you are suffering from PH issues. Lower your PH to a more stable 6-6.3. So are great for taking swings in PH but if you have been giving that PH you could be causing unwanted issues like nutelock. With soil, the watering feeds are just as important as the nutes. As your water feeds come behind your feed and pick up and excess nutes/salts in the soil. Try cute down on nutes. You don't need such heavy doses with soil. 1ml/l at that stage is enough or 7-900ppm max. You can push 2 1400 if your plant can take it in later stages, much later, but always get there say in 100ppm increases or even 50's at a time. And 2 feeds max per wk. Other 2 should be water in between so 4 feeds over 8 days about 150-200ml either nutes mix 2 a wk spread em out and water in between. Best of luck pal.