Help, my leaves are dieing, I think I may have bee...

For slugs and snails, use cooper stripes, they have some kind of allergic reaction to it, or beer traps, they drown on it; crushed egg shells help keep them away too. There are many things that can be factoring on your plant dying: pH out of range, since you are not meassuring it, much less adjusting it; too much nutrients, your trouble started when you upped the dose to 4 ml of biogrow, 4 ml of biobloom and 1ml of fishmix, that can easily be around 2.5EC/1250 PPM (I use biobizz), give them plain water for now, or better yet, give them a light flush and dial back the nutrients after that. For reference I never go higher than half that concentration or I start having trouble; third and foremost, temperatures, you are having dangerous fluctuations and go from really cold at night to really hot during the day. 5°C is too cold, hell 15°C is too cold and 50°C during the day... Unless you can keep them under better temperatures they are going to suffer, a lot.