Let me just clarify ... are these the recommended dosages as per the bottle?? If so that may be where your problem lies. I start EVERY new nutrient feeding I`d be unfamiliar with a 1/4 strength of the recommended dosage. Remember less is more in the first couple weeks of flower.
Do you have anything to get a PPM reading on your feedings as that would also give me a better idea, but that is nute burn for sure unless those leaveshave come into contact with the light at some point. Get some more info up and I`d be glad to help mate. Happy growing
KC
**EDIT - would recommend a 3-4 day flush my friend in the meantime and resume your schedule for week 5 at 3/4 strength, you should see MUCH improvement

**