all i know is to wash and repot with different soil as in new soil i don't know how they got there but after you wash and repot KEEP AWAY! from other plants until about a week of no Aphids you don't want any more infected plants and if you use the same pot wash it to... you don't want those tricky things to come back P.S. they multiply quickly so do it as quick as possible

-Blake

Flavia - sometimes all you need to do is blast the aphids off of your plants with a strong stream of water. The second picture looks like it may be mealies on the stem. You can remove those from your plant with a cotton swab dipped in rubbing alcohol (isopropyl alcohol). They will turn a reddish color!

In either case - aphids or mealies - spray the plants with a 50/50 solution of rubbing alcohol and water. Keep the plants out of direct sun while treating to they don't burn. Repeat the spray in a few days. Keep an eye out for their return and repeat the process if necessary.

Good luck!