Gardener bots issues

I have Eco life and university. I have three gardener bots in my greenhouse. One of my gardener bots insists on watering one of the alien plants non-stop. I got tired of this so I changed the planter boxes to the self watering type and the gardener bot is still watering the same alien plant. Now a second gardener bot is watering another plant in one of the self watering planter boxes. They're neglecting the trees that are not in the self watering boxes.
Also I have a large greenhouse and it seems like it takes forever for those bots to finish watering anything.
Are they bugged or something?