Help!  My babies are dying.  I've got two large psychotria alba trees, and one sapling alba, and they're all losing leaves at a prodigious rate...I left to visit my family yesterday and 30-40 leaves were scattered around the floor when I came back today.

I've been wintering them in my living room since October.  Last week I let them out for two days, but after the first they started to look sick and when they got worse the second day I took them back inside.  Since then they've been seeming to get worse and in the past couple of days have started dropping leaves...I don't know what's happening, they're back in the same environment they had been thriving in all winter.  It was windy and in the 60's in the evenings when I had them outside for those 2 days, but it's been in the 60's in my house over the winter as well.

Their soil is moist, they're getting sunlight, and my viridis, which has been hanging out alongside them, is perfectly healthy...I don't know what's happening.  I bought some fertilizer today because that's the only thing I can think of to do, but I don't know much about plants and am afraid if I give them some that'll make them even more sick somehow.  It's back in the 70's today, should I send them outside again or will it make them worse again?  Any help or advice is appreciated...this is breaking my heart.