I'm sorry to hear of this with Skittle, Raul. At such a young age he's likely to be malnourished, septic (widespread infection - bacterial or viral, mainly), or both.
An avian-oriented vet (please see here: www.aav.org) is essential at this time and might first treat symptomatically and supportively by providing supplemental fluids and electrolytes by needle and tube feeding a "recovery" food. Blood tests and cultures of Skittle's choana - the slit between his oral cavity and nose - and cloaca (vent) may be taken. Whole body X-rays can be quite helpful as well. The vet will consider common pediatric disorders such as crop stasis ("sour crop") due to systemic illness, chilling, or dehydration; thermal injuries to the crop, gram negative bacterial infections, fungal (Candida, Aspergillus) infections, viral (polyomavirus, adenovirus, PBFD) infections, and protozoal (Trichomonas, e.g.) infections.
Until Skittle can be attended to, please heat up his environment to 85F by means of a 100W bulb shined into his partially covered cage (not at night when he needs to rest) or by taping a heating pad set on its lowest setting to the sides of his cage. Time is of the essence in these fledglings.
Please respond with further questions or concerns if you wish.