Yellow leaf tips and edges

Nutrient burn, feeding too much, too often - half strength is usually enough. Damaged leaves will stay damaged. Try not feeding for 10 days, judging by the dark green colour, there should be enough residual nitrogen in the substrate to keep them going for that long at least. Flushing can actually cause more nitrogen to become freely available and then cause even more burning, so just plain water and in normal amounts for the next ten days and definitely no feeding if you want to get your planrts back on track. Try a schedule of plain water/plain water/feed, so that you are only feeding every 10-12 days and this is plenty in soil. Hope this helps, Organoman.

it seems that plant is not in the right conditions, try to increase humidity to 50% at least . and feed as usual, remember less is more.

I would say she is starting to need some more phosphorus and potassium mate.