Hello, my philodendron 'Silver Sword' recently had some of the lower leaves begin to turn yellow. They used to all be the same silvery colour for a while, while I would water the plant near weekly under grow lights from the pole until I left for vacation (for a little over a week) and asked my parents to water my plants. They did wonderful with all my plants but I don't think they watered the pole for my silver sword as thoroughly as I do. The day before I returned the lower leaves quickly began turning yellow. I have since given it a proper watering (three days ago) and it continues to slowly go more yellow. Should I take any more action? Does this seem like underwatering, overwatering it or neither (I haven't really fertilized it before I don't know if that could be part of the issue)? Any and all help is greatly appreciated, I'm not so great with aroids. Thanks!! (photo 2 is where I leave the plant)