Hector- Plagron is mild stuff,... this is the "algae" line-- 2-4-2 and 3-2-5 ? ...given your 1/4 str. dosing, and ok pH (could come up to 6.5 preferably), i think you have a couple deficiencies going,... interveinal yellowing suggests Mg defc., and the tip/teeth necrosis, looks like K defc. to me, too,.... there is some overlap with the yellowing between them,... I suggest upping your nute conc. to at least half, and see how they react, and start with some dedicated Ca-Mg product too, to cover the bases,... I looked at Plagron's site, and the info for grow and bloom is weird, like they mixed up the NPK nubers between them...? ...grow is 2-4-2; bloom 3-2-5...??! looks backwards in ratio's to me! :dunno:...do you have a P-K booster? double check your bottles for me too please, and see what the NKP#'s are on them,... then we can dial in a treatment plan,...