Female Swordtail Thinning Very Quickly

[-FighterFishh]

One of my swordtails in my 30L biorb is thinning extremely quickly, and has all her fins clamped.
She's been like this for a couple of days now.
She's been eating fine, and I've watched her get food, but then she just hides round the back, in plants, or hangs at the top.
She must have given birth at one point, as there is a baby sword swimming round in the tank that's the same colour as her.
Can anyone help me save her?
Thank you for any advice.

 

[BeckyJay]

Looking thin, hiding, clamped fins, these are all symptoms of internal parasites. Are there any other symptoms, white poo? colour loss? spitting out food?