IMO i think its over watered and under fed, the leaf should be a nice equal green throughout not light with dark veins thats a sign they are hungry, but the droopy leaf look is over water, let it fully dry out till the pot feels like a feather then FEED the poor thing
dont over do the feed, just follow what the bottle says probs 1ml:1L
try to water with 500ml-1L after it has fully dried out, and see how long that lasts
i water my plants 1L every morning and i seem to be on the perfect wet/dry routine
and i, water, feed, water, water, feed, water, feed sort of thing, unless the leaves start to look to dark green then the N is being overdone a bit,
they way i work it out is, feed them and then once the tips of new growth start to become a light yelowish colour, dont feed for a couple of days let them use what they have at that point, so your just on the verge of nutrient burn but not getting it