I have 4 male guppy's in my 20 gallon tank along with 2 molly's (1 male and 1 female), and two male black phantom tetras. march 20th will be adding one more female molly and one more male black phantom tetra. My question is within the last few weeks two of my guppy's ,the yellow and the turquoise, their stomachs have gotten fat. i mean if they were females i would think they were pregnant. lately the turquoise one likes hiding in the corners at the bottom of the tank behind plants. before the yellow one got fat he was sick i think because he just sat at the bottom of the tank and was shrinking. we did a couple of water changes and he started moving around more and now he has gotten fat like the turquoise one and now hangs at the top of tank in the corner. the two orange guppy's are fine. are they sick? im new to fish so i dont know whats going on. plz help if you can. i will include two pics of the turquoise and 1 of the yellow guppy and one of the orange one just to compare.