2.5 gall
WATERING VOLUME PER PLANT PER 24H
Are you really giving them so much? 5 l in two days for all or per one? Have you heard of DWC?
Burnt tips might be really nutes overdose. You can always wash soil till quite clean water runs out of the pot. Many people wash soil before flowering and then go to flowering nute schedule. and then flush again every 2-3 week. It is the simplest way to get rid of wrong feeding consequences. You might feed well, but in this case it could be particular plant trait, or soil salinization. 👌