Hello all!! I'm a pretty new plant Mama, in the last year I've become completely addicted, lol. This time last year, I bought these two gorgeous monsteras at Target at 50% off, and I've not been the same since, lol. They've remained my favorite (we now have 96 plants and about 2 dozen props of ALL different species). These gals have become huge in that time and today I had my first yellow leaf (I snipped it before taking the pics) and that told me that I'm no longer doing what they need to thrive. I'm not great at propagating, mostly because I'm nervous (all of my props have a ton of roots, and I'm terrified of killing them once taken out of their prop vases and put into dirt).  Today I gave them their first fertilizer ever, but it's miracle grow and I have a feeling that it's probably not the best and I'd prefer to get them the best. So I'm looking for recommendations on both fertilizer as well as advice as to what I should do to make sure that these beauties continue to get more gorgeous. I water them in the sink in their nursery pots once a week and only put them back in their pots once all of the excess water has drained, I switch their positions every time I put them back. They currently live above our mantle and have 2 huge skylights above them about 8' away from them. So opinions, and advice are very welcome. Also, please be nice, I'm truly trying my best, but I see so many opposing things online and I don't know that to trust. Thank you in advance for your time!!! Their named Thelma and Louise, btw. 

What should I do?