The roots are seeking upward because it's too wet below. RW is highly absorbent and can not tolerate frequent watering. Your droop is likely root rot beginning, due to overwet media.
Watering from the top means you have nice yummy plant food and water on a medium that is exposed to light. Any passing algae spore is likely to find it rather hospitable. Don't top water and the problem will never start. Once you have algae on the media tops, it'll be fairly hard to get rid of completely, but don't stress. It's on the top of the media, not in the plant's rootmass, so no harm done. Like any plant algae needs food, water & light. Take away as many as you can and it will slow or stop. Block light with a disc of panda film with a hole for the plant's stem and a slot on the radius for fitting.
Flood your RW blocks 1x/lights-on for about 1-2mins. That will be sufficient until the plants recover and grow more vigorously.
Treat your nute soln with 50% grade H2O2 @ 1ml/L every 3-4 days, will help fix the root probs, oxygenates the roots and will kill smaller colonies of algae.
