Hello again, the plants are getting worse..

I have now done an accurate soil runoff ph test, came out at 6.6, tested my tap water and was 6.8

So what are my options to bring the plant back to health, as now into week 7 of flowering I cant add any nutes,

Bit worried about one of the other plants now, is getting the same bright yellow patches on the tips of the leaves around the buds, on the really sick one (in the pictures) the problem doesnt seem to have spread to the buds yet and remains on the larger top leaves, although the problem is getting worse

Any help would be apreciated

Thanks