Royal Cheese - Photo - Royal Queen Seeds

Got some leaf taco ing, and a two of the plants have developed some yellow leaves, burnt tips, I don't think it's nute burn as amount of nutes watering every 2 to 3 days is very low, I thought possibly potassium deficiency, increased fish mix slightly, the yellowing is not effecting the top leaves only so I didn't think light burn, I've moved the light up a few inches to be on safe side and turned power down from 70 percent to 60 percent, using photone app to measure DLI/par intensity and reading about 700 so possibly too high. Gonna flush the two plants worse effected, PH testing RO filtered water to 6.5, also added a bit of cal mag, hopefully following the flush, should sort itself. Any advice greatly appreciated fellow growmies :)